Olefin oxidation catalyst system

ABSTRACT

The additional of redox-active metal components and ligands, alternatively or simultaneously, results in increased conversion and selectivity in the palladium-catalyzed oxidation of olefins to carbonyl products in the presence of polyoxoanions. In preferred modes, heteropolyoxoanions and Isopolyoxoanions containing tungsten, molybdenum and vanadium, individually or in combination, are described. The use of copper as the redox-active metal component shows reduced allylic reactivity. The elimination of chloride from the catalyst system provides substantial engineering advantages over the prior art, particularly, the reduction of corrosion and chloro-organic by-product formation. The use of redox-active metal components and/or ligands makes the palladium-polyoxoanion catalyst system industrially practicable.

This is a continuation of application Ser. No. 06/779,501, filed Sept.24, 1985 and now U.S. Pat. No. 4,720,474.

DESCRIPTION

1. Technical Field

This invention relates generally to palladium catalyzed oxidation ofolefins to carbonyl compounds. More specifically, this invention relatesto the use of heteropolyoxoanions and isopolyoxoanions in a one stageliquid phase oxidation of olefins with molecular oxygen. The addition ofredox active metals and ligands, alternatively or simultaneously, to thecatalyst system improves conversion and selectivity to the desiredcarbonyl products.

2. Background of the Invention

The catalyst compounds and systems of the present invention are usefulin the production of ketones which are important industrial commoditychemicals. For example, methyl ethyl ketone and methyl isobutyl ketonefind use as solvents. Further the present invention can be used to makeheretofore unavailable ketones which can serve as new classes of usefulspecialty chemical products, or intermediates used in their production.

Palladium catalysts are useful in the oxidation of unsaturatedhydrocarbons. One large class of hydrocarbons is olefins. Depending onthe catalyst composition and reaction conditions, a number of differentmajor reaction products may result. The generalized examples are:##STR1##

A good summary of palladium catalyzed olefin oxidations can be found inChapter 7 of "Metal-Catalyzed Oxidations of Organic Compounds" bySheldon and Kochi (Academic Press, New York, 1981). A more specificreview, "Synthetic Applications of the Palladium Catalyzed Oxidation ofOlefins to Ketones" has been written by J. Tsuji; Synthesis 5, 369-384(1984).

In the oxidations outlined above, Pd⁺² is reduced. The overall reactionscan be made catalytic if the palladium can be reoxidized by an oxidizingagent. Preferentially, one would use plentiful and cheap oxygen fromair. The direct reoxidation of palladium by oxygen is thermodynamicallypossible but kinetically too slow. As a result, a co-catalyst isrequired to speed up the overall oxidation process.

The Wacker-type oxidation process of the prior art uses PdCl₂ /CuCl₂ asthe catalyst system where Cu⁺² plays the role of the co-catalyst.

    Pd°+2CuCl.sub.4.sup.-2 →PdCl.sub.4.sup.-2 +2CuCl.sub.2.sup.-( 5)

    2Cl.sup.- +2HCl+1/20.sub.2 +2CuCl.sub.2.sup.- →2CuCl.sub.4.sup.-2 +H.sub.2 O                                                (6)

It should be noted that the copper is necessary to improve palladiumreoxidation kinetics. Chloride (Cl⁻) is an essential ingredient since asa Pd⁺² ligand, it provides a driving force for reaction (5) and, as aCu⁺² ligand, it makes reaction (6) possible.

The above Wacker system, however, presents several substantialengineering problems making commercial application difficult. The use ofchlorides results in severe corrosion, requiring the use of expensive,i.e. titanium-clad, reactor vessels. Further, the presence of chlorideions results in the formation of undesirable chlorinated byproductswhich lowers the overall yield of desired material. In addition, thesechlorinated by-products often prove difficult to separate from thedesired product.

In response to these unfavorable characteristics of Wacker-typecatalysts, new systems have been developed by others to reduce the levelof chloride present in the olefin oxidation system. The best examples ofthese newly developed systems can be found in Belgian Pat. No. 828,603,the work of Ogawa et al., J.C.S. Chem. Comm, 1274-75 (1981), and U.S.Pat. No. 4,434,082.

Belgian Pat. No. 828,603 (Oct. 30, 1975) teaches the use ofpolyoxoanions as co-catalysts to regenerate Pd⁺². The reducedpolyoxoanions are subsequently reoxidized with oxygen. Suchpolyoxoanions can be generally described in the following way.

In aqueous solution certain metal oxides undergo stepwisehydrolysis-oligomerization reactions upon acidification according to thefollowing representative stoichiometries ["Heteropoly and IsopolyOxometalates" by M. T. Pope (Springer-Verlag, New York, 1983)]: ##STR2##where bn+cq=y+a (oxygen atom balance)

br+cs-2a=p (charge balance)

and where M can be one of several metals, e.g. W, Mo, V, or mixtures ofthese metals. X is usually P or Si but can be a number of otherelements. The condensed metal oxides, e.g. [X_(c) M_(b) O_(y) ]^(-p),form a symmetric three dimensional array whose structure and compositioncan vary a great deal with various X's and M's. Which structure ispresent depends on the acidity of the solution, the initial amounts ofMO_(n) ^(-r) and XO_(q) ^(-s), and other reaction conditions. In somecases, even under the same reaction conditions, different structures maybe present. Products formed by reaction (7) are called isopolyoxoanions.Products formed by reaction (8) contain a "hetero" atom X, usuallycentrally located in the structure, and as a result these products arereferred to as heteropolyoxoanions. Hereinafter, polyoxoanion (POA) maybe used to refer to heteropolyoxoanions and isopolyoxoanions. Thoseskilled in the art would be capable of differentiatingheteropolyoxoanions from isopolyoxoanions when necessary for clarity.

The Belgian patent discloses a number of heteropolyoxoanioncompositions, mostly containing mixtures of molybdenum and vanadium,useful in the oxidation of ethylene to acetaldehyde, propylene toacetone, butene to methyl ethyl ketone and 1-hexene to 2-hexanone. It isalso disclosed that isopolyoxoanion compositions can lead to unstablecatalyst systems. Further, it is disclosed that an increase in thenumber of vanadium atoms from one to six is observed to cause anincrease in the beneficial characteristics of the catalyst, whichcatalyst can be prepared in situ without isolation.

High selectivity is predicted for a large number of olefins but onlyshown for C₂ to C₄ in which cases isomerization either cannot occur(C₂), occurs to give the same structure (C₃), or occurs to givedifferent isomers which react to the same product (C₄) as shown inequation (9). ##STR3##

The examples disclosed in the Belgian patent show that when 1-hexene isused, selectively to 2-hexanone drops significantly due toisomerization.

The iso- and heteropolyoxoanions of the instant invention, e.g. PMo₆ V₆O₄₀ ⁻⁹, PW₆ Mo₆ O₄₀ ⁻³, P₂ W₁₅ V₃ O₆₂ ⁻⁹, are used in conjunction with aredox active metal and (or) a ligand for the redox active metal and (or)the palladium component. The addition o the redox active metal componentand the ligand, either singly or in combination, results in greatlyimproved conversions and selectivities not taught by the prior art.

The Belgian patent teaches the use of the polyoxoanion component and thepalladium component in ratios of 100:1-1000:1, which leads to very highPOA loadings. Lower ratios (2:1 and 33.3:1) require high palladiumconcentrations. The instant invention reduces the amount ofisopolyoxoanion or heteropolyoxoanion required such that favorablecatalyst activity is observed when polyoxoanion:Pd ratios of 0.5:1-10:1are used. The disparity in co-catalyst (POA) loading between the Belgianpatent and the instant invention is partially attributable to the factthat the overall oxidation process disclosed in the Belgian patentrequires two stages.

In the first stage of that process, the palladium component oxidizes theolefin. In order to achieve commercially acceptable turnovers of theolefin on palladium, large molar amounts of polyoxoanions are required.This results from the fact that the reaction is stoichiometric in thepolyoxoanion due to the absence of molecular oxygen. As a result of thehigh molecular weight of these compounds, large masses of thesecompounds are correspondingly loaded, rendering commercial operationimpractical from solubility, viscosity and catalyst distributionstandpoints. Once all the polyoxoanion is reduced, the palladium canprecipitate out as the metal (zero valent state). In the second stage,after removal of hydrocarbons, oxygen is added to reoxidize thepolyoxoanion.

The favorable catalyst activity of the instant invention enables a onestage oxidation process. While a proper choice of thehydrocarbon/oxidant feed composition and proper reactor design caneliminate potential safety hazards, a one-stage process not onlyeliminates the need for a second stage, but also eliminates theengineering problems associated with the handling of high viscosityfluids resulting from the use of high polyoxoanion concentrations. Theaddition of a redox active metal and (or) ligand for the palladium and(or) the redox active metal, not only further reduces the amount ofheteropolyoxoanion needed, but in a number of cases these additivesproduce active polyoxoanion systems from otherwise inactive ones, e.g.,P₂ W₁₂ Mo₆ O₆₂ ⁻⁶, which by itself does not reoxidze with oxygen. Inaddition, the presence of a redox active metal and (or) ligand,unexpectedly increases the olefin oxidation rate and also improves theselectivity and yield to the desired carbonyl product. Furthermore, byusing less polyoxoanion, the cost of the catalyst per unit ofhydrocarbon product is reduced substantially.

The Belgian patent teaches the use of PdCl₂ and PdSO₄. Although thechloride levels are greatly reduced or supposedly eliminated as comparedto the PdCl₂ /CuCl₂ system, the patent further teaches the use ofpolyethylsiloxane as a corrosion inhibitor. Thus it is obvious that atthese high polyoxoanion concentrations, the corrosion problem ofWacker-type systems has merely been mitigated. The catalyst systems ofthe instant invention do not contain chloride ions except sometimes aseventual trace contaminants introduced during polyoxoanion synthesis.These systems do not significantly corrode commonly used steels,resulting in substantial capital savings in plant construction.

Vanadium-free heteropolyoxoanion compounds useful in olefin oxidationsare disclosed in "Liquid Phase Oxidation of Cyclo-olefins by a PdSO₄-Heteropolyacid Catalyst System" by Ogawa, Fujinami, Taya and Teratani,J.C.S. Chem. Comm., 1274-75 (1981) The catalyst system of interest isPdSO₄ --H₃ PMo₆ W₆ O₄₀ for the oxidation of cyclohexane tocyclohexanone. Very limited conversions were attained, indicating thatthe reoxidation of Pd° to Pd⁺² was very inefficient. These systems donot possess commercially viable catalyst lifetimes, especially in viewof the high cost of palladium.

The instant invention teaches that the use of a redox active metalcomponent, (and) or a ligand component, in conjunction with the Pd⁺² /H₃PMo₆ W₆ O₄₀ system improves the conversion and selectivity. However, inthe above mentioned particular case of H₃ PMo₆ W₆ O₄₀, addition of botha redox active metal component and a ligand increases the oxidation rateby more than two orders of magnitude. This surprising result permitspractical application of this catalyst system in an industrial process.

If the redox active metal component is copper, then selectivity to thecarbonyl reaction product is greatly improved while copper inhibits theallylic oxidation pathway. This is important in the case of thoseolefins that have reactive allylic positions, e.g. cyclohexane: ##STR4##

U.S. Pat. No. 4,434,082 (Feb. 28, 1984) (hereinafter '082) teaches aPd⁺² -heteropolyoxoanion-surfactant system useful in olefin oxidation toketones. A two phase system is employed consisting of an aqueous phaseand a hydrocarbon phase. In such a system, the olefin tends to stay inthe hydrocarbon phase and the catalyst in the aqueous phase. As aresult, the yields of oxidized product, as shown in Example 6 of the'082 patent, are below three percent for the oxidation of 1-butene tomethyl ethyl ketone in the absence of surfactants. To improve thereaction kinetics, the surfactant component is essential for bringingthe catalyst and reactants into intimate contact. The instant inventionshows improved conversions and selectivities without the use of thissurfactant component, identified as essential in the '082 patent.

In sharp contrast to the catalyst of the prior art, the use of thecatalyst system of the instant invention results in a more efficientoxidation process from several important process engineeringperspectives. The conversion and selectivity to the desired carbonylproduct are greatly improved over earlier systems wherein polyoxoanionswere used. Catalyst lifetimes are also enhanced in the present systems.This permits the use of less catalyst, resulting in significant savings.Additionally, the present catalyst systems can be used in a single stageoxidation process, reducing process costs for the energy required topump and heat the reactants and catalysts, as well as capital equipmentcosts for the second stage process equipment.

The use of chloride-free components eliminates several major engineeringshortcomings of the Wacker systems of the prior art. In particular,chloride-free systems exhibit no corrosivity to the process equipment,making the use of stainless steel process equipment possible. Thisfactor improves process economics substantially because initial capitalcosts for stainless steel equipment are far below those fortitanium-clad or glass-lined vessels. Further, chloride-free systemseliminate many of the problems resulting from chloroorganic by-productformation under oxidation process conditions. The separation anddisposal of these undesirable choloroorganic compounds presentsignificant engineering and environmental problems when encountered onan industrial process scale.

The present catalyst system exhibit higher yields than the prior artwhen more complex substrates are oxidized. Chloride-containing catalystsshow a pronounced and rapid dropoff in yield of the desired carbonylcompounds ad the number of carbons in the olefin substrate increases.The formation of complex chloroorganic by-products decreases overallyield to the desired carbonyl product. In the present system, thedecrease in yield as a function of the increasing number of carbons inthe olefin is less pronounced. This allows the economically attractiveproduction of ketones which could not be produced by prior art catalystsystems.

Therefore, it is one object of this invention to provide an efficientcatalyst system for olefin oxidation which eliminates the use ofcorrosive chloride ions.

It is another object of this invention to provide a catalyst systemwhich possesses economically practicable industrial oxidation rates,conversions and selectivities.

It is yet another object of this invention to eliminate the use of aphase transfer agent or surfactant in the reaction system.

It is a further object of this invention to obtain improved rates andselectivities in the olefin oxidation reaction by the use of a redoxactive metal component and/or the use of a ligand.

It is another object of this invention to be able to oxidize a largenumber of olefins which could not be oxidized efficiently previouslybecause of one or more of the following problems: (a) isomerization, (b)chlorinated by-product formation, and (c) oxidation rates which are toolow for industrial practice.

SUMMARY OF THE INVENTION

In accordance with the present invention, catalyst systems useful inolefin oxidation to carbonyl compounds are disclosed. The catalystsystems generally comprise at least one polyoxoanion component and apalladium component. Marked improvements in conversion and yield areobtained when redox active metal components and ligands are added to thesystem, either alternatively or simultaneously.

The polyoxoanions of the present invention are of two general types.Heteropolyoxoanion compounds are disclosed wherein the "hetero" atom is,e.g., phosphorus, which is surrounded by molybdenum, vanadium, tungsten,individually or in combination, and oxygen atoms. The second type ofpolyoxoanion is an isopolyoxoanion or a mixed isopolyoxoanion ofmolybdenum, vanadium, tungsten and oxygen atoms.

The palladium component of the catalyst system can be introduced viapalladium metal or a chloride-free palladium compound. The redox activemetal component of the present invention is generally a metal anioncapable of changing its oxidation state under olefin oxidation reactionconditions. Typically, compounds of copper, iron and manganese areuseful as the redox active metal component.

The ligands useful in the catalyst system of the present invention areselected from the family of nitrile compounds. The ligand interacts withthe palladium component and (or) the redox active metal component, whichenables one, in a substantial number of cases, to increase the rate ofolefin oxidation, and (or) the selectivity, and (or) the lifetime of thecatalyst.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plot of the rate of α-olefin oxidation versus the number ofcarbon atoms in the α-olefin.

FIG. 2 is a plot of SS316 corrosion rates versus chloride concentration.

DETAILED DESCRIPTION OF THE INVENTION A. Theoretical Basis

The catalyst utilized according to the instant invention for theoxidation of olefins is made up of the following components: (1) apalladium component; (2) at least one polyoxoanion component; (3) aredox active metal component; and (or) (4) a ligand, where the ligandcan complex with either the palladium and (or) with the redox activemetal.

The overall general reaction scheme for a representative olefinoxidation can be written as follows: ##STR5##

In the above scheme, ##STR6## represents any olefin, and water isrepresentative of the many nucleophiles which can be used. Ligands L andL' can be the same ligand or can be different ligands. These ligands mayinclude a solvent component or a metal counterion. M_(r) ^(+q)represents the redox active metal component which can undergo a changein oxidation state. POA^(-p) represents any polyoxoanion including theircounterions. Similarly, H⁺ can be generated by any of a number ofsources, including, but not limited to acids and water.

Ligand L should possess the following properties. It should complex withpalladium (+2) without eliminating the formation of the olefin-Pd⁺²complex as shown in equation (11). Thus one would expect that ligands Lwhich are not very strong complexors of Pd⁺², and especially ones whichdo not have multiple binding sites for Pd⁺², would be desirable.

Further the ligand L must not reduce the positive charge on Pd⁺² to thepoint where reaction (12) becomes too slow. Electron poor ligands whichcan remove negative charge easily from Pd⁺² would be preferred ligands.

Ligand L on the other hand should be a strong enough complexor of Pd⁺²to give additional thermodynamic driving force for reaction (15). In thebest case, such a ligand L would stabilize [PdH]⁺ long enough [Equation(13)] so that it could be oxidized with oxygen before it decomposed toyield palladium metal by reaction (14). It would then allow palladium tobe reoxidized without the need for separate reoxidation systems asrepresented by equations (15) and (16).

As shown above, there is a delicate balance between several effects andonly a limited number of ligands L will improve the overall reaction.Others can, and will, slow down or stop the oxidation. The ligands founduseful in this invention are described with greater specificity inSection B(4) below. A POA^(-p) when used by itself must accomplish twofunctions. First, it must be able to accept electrons from Pd° andoxidize it [Equation (15)]. Then, once reduced, the POA^(-p-2) must beable to reduce oxygen so that the catalytic cycle continues [Equation(16)]. There are a large number of POA's which cannot do botheffectively. The redox active metal as shown in the followingcombination

    [POA.sup.-p +M.sub.r L'.sub.m.sup.+q ].sup.-p+q            (15)

is designed to overcome this shortcoming of many of the polyoxoanions.Its function is, either independently, or in conjunction with thepolyoxoanion, to improve reaction (15) and (or) reaction (16). Ligand L'has to be chosen in such a way that the thermodynamics (driving force ofthe reaction) and the kinetics (speed at which the reaction takes place)are both favored. In some cases the same species can act as ligand L forPd⁺² and ligand L' for M_(r).

The above thermodynamic and kinetic requirements can only be met if theability to transfer electrons between M₂ L'_(n) ^(+q) and (or) POA^(-p)and Pd° and (or) O₂ exists.

Electrochemistry is one way of analyzing whether the particular PdL_(n)⁺² /POA^(-p) /M_(r) L'_(n) ^(+q) combination is potentially a goodcatalyst system. Useful combinations preferably have oxidation-reductionpotentials (E°_(1/2) 's) for PdL_(n) ⁺² +2e Pd°+nL, M_(r) L'_(m) ^(+q+2)+2e M_(r) L'_(m) ^(+q) and POA^(-p) +2e POA^(-p-2) within the potentialrange of +0.7 VOLT to +0.2 VOLT versus SCE. While the E°_(1/2) 's of theindividual catalyst components may not be in the 0.2-0.7 Volt range, theE°_(1/2) of their combination will lie in this range as the result ofinteractions. Further, the oxidation-reduction potential of [POA^(-p)+M_(r) L'_(m) ^(+q) ]^(-p+q) +2e [POA+M_(r) L'_(m) ]^(-p+q-2) should bechosen to be greater than or close to PdL_(n) ⁺² +2e Pd°+ nL and lessthan the potential of the reaction 1/20₂ +2H^(++2e) H₂ O.

It has been found that the catalyst systems of the present invention areespecially effective when the E°_(1/2) 's for the individual catalystcomponents are roughly of the same magnitude, i.e +0.35 ±0.1 VOLT versusSCE.

The overall reaction (17) is acid independent. However, some of itscomponent steps [(12), (14), (16)] are acid dependent. Consequently, onemay have to adjust the pH (acidity) to obtain the best overall oxidationrate.

Selectivity to the desired carbonyl product can be decreased by sidereactions of the olefin such as isomerization by pathways shown inequations (11') and (13'). Overoxidation of the product is alsopossible. ##STR7## The above side reactions can be catalyzed by thecomplexes and compounds shown in equations (11) to (16) or by otherunidentified catalytic species which form under the reaction conditions.

It can be a further benefit of ligand L, and (or) L', and (or) theredoxactive metal M_(r) ^(+q) that these ligands and metals reduce therates of some or all of the above undesirable side reactions. Forexample, by increasing the rate of reaction (12) with respect to therate of isomerization of ##STR8## [reaction (11')] a higher selectivityis obtained.

Changing the ligands L and (or) L', and (or) the metal M_(r) ^(+q) willcause one to observe worse or better results, depending on how theyaffect the various reaction steps (11) to (16) and (18). Thus if one canrapidly eliminate an isomerization catalyst such as [PdH]⁺ by equation(19)

a better yield to the desired product is the result.

Another example would be if the [POA^(-p) +M_(r) L'_(m) ^(+q) ]^(-p+q)oxidizes ##STR9## before it decomposes to Pd°. Then increasing the ratesof reactions (15) and (or) (16) would reduce isomerization.

In a similar fashion, changing L, and (or) L' and (or) M_(r) ^(+q) willchange the amount of other side reactions such as overoxidation.

Optionally, M_(r) ^(+q) and (or) Pd⁺² can be part of the polyoxoanionstructure.

B. Catalyst System

The catalyst system of the present invention generally comprises atleast one polyoxoanion component and a palladium component. The additionof a redox-active metal component, and (or) a ligand increases theconversion of olefin and selectivity to the desired carbonyl product.

(1) The Polyoxoanion Component

The polyoxoanion component of the catalyst system can be either anisopolyoxoanion or heteropolyoxoanion of niobium, tantalum, rhenium,molybdenum, vanadium and tungsten, either in combination orindividually. The "hetero" atom can be boron, silicon, germanium,phosphorus, arsenic, selenium, tellurium, iodine, cobalt, manganese orcopper. Both polyoxoanion types can be described by the general formula:

    [X.sub.x M.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member chosen from the group consisting of B, Si, Ge, P,As, Se, Te, I, Co, Mn and Cu;

M, M' and M" are members independently selected from the groupconsisting of W, Mo, V, Nb, Ta and Re;

x is zero for isopolyoxoanions and mixed isopolyoxoanions or x is aninteger for heteropolyoxoanions;

a, b, c, m and z are integers; and a+b+c≦2. Several sub-genera ofpolyoxoanions have also been developed to describe the polyoxoanioncomponents of the instant invention.

I. Isopolyoxoanions A. General

    [M.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M, M' and M" are members independently selected from the groupconsisting of W, Mo, V, Nb, Ta and Re; z and m are integers greater thanzero; a, b and c are integers; and a+b+c≦2;

B. Molybdenum

    [Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein

M' and M" are members independently selected from the group consistingof W, V, Nb, Ta and Re; a, z and m are integers greater than zero;

b and c are integers; and a+b+c≦2;

C. Tungsten

    [W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein

M' and M" are members independently selected from the group consistingof Mo, V, Nb, Ta and Re; a, z and m are integers greater than zero;

b, c are integers; and a+b+c≦2;

D. Vanadium

    [V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein

M' and M" are members independently selected from the group consistingof W, Mo, Nb, Ta and Re; a, z and m are integers greater than zero;

b, c are integers; and a+b+c≦2;

II. Heteropolyoxoanions A. General

    [X.sub.x M.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu;

M, M' and M" are members independently selected from the groupconsisting of W, Mo, V, Nb, Ta, Re; a, x, z and m are integers greaterthan zero;

b, c are integers; and a+b+c≦2;

B. Molybdenum

    [X.sub.x MoaM'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu;

M' and M" are members independently selected from the group consistingof W, V, Nb, Ta and Re;

a, x, z and m are integers greater than zero;

b, c are integers; and a+b+c≦2;

C. Tungsten

    [X.sub.x W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu;

M' and M" are members independently selected from the group consistingof Mo, V, Nb, Ta and Re;

a, x, z and m are integers greater than zero;

b, c are integers; and a+b+c≦2;

D. Vanadium

    [X.sub.x V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu;

M' and M" are members independently selected from the group consistingof W, Mo, Nb, Ta and Re;

a, x, z and m are integers greater than zero;

b, c are integers; and a+b+c≦2;

Examples of typical polyoxoanion species are as follows:

(a) Heteropolyoxoanions.

    [PMo.sub.6 V.sub.6 O.sub.40 ].sup.-9

[PMo₄ V₈ O₄₀ ]⁻¹¹

[PMo₈ V₄ O₄₀ ]⁻⁷

[P₂ W₁₂ Mo₅ VO₆₂ ]⁻⁷

[P₂ W₁₅ Mo₂ VO₆₂ ]⁻⁷

(b) Isopolyoxoanions.

[Mo₄ V₈ O₃₆ ]⁻⁸

[Mo₃ V₃ O₁₉ ]⁻⁵

[Mo₆ V₂ O₂₆ ]⁻⁶

[Mo₆ V₆ O₃₆ ]⁻⁶

[W₇ Mo₃ V₂ O₃₆ ]⁻²

[Mo₈ V₄ O₃₆ ]⁻⁴

(c) Vanadium-free polyoxoanions.

[P₂ Mo₁₈ O₆₂ ]⁻⁶

[P₂ Mo₆ W₁₂ O₆₂ ]⁻⁶

[PMo₆ W₆ O₄₀ ]⁻³

[P₂ Mo₅ O₂₃ ]⁻⁶

[Mo₆ W₆ O₄₁ ]⁻¹⁰

(d) Molybdenum-free polyoxoanions.

[PV₁₄ O₄₂ ]⁻⁹

[PWV₁₁ O₄₀ ]⁻¹⁴

[PW₆ V₆ O₄₀ ]⁻⁹

[PW₈ V₄ O₄₀ ]⁻⁷

[P₂ W₁₂ V₆ O₆₂ ]⁻¹²

[P₂ W₁₅ V₃ O₆₂ ]⁻⁹

[W₆ V₆ O₃₆ ]⁻⁶

It is to be recognized, by one skilled in the art, that even though aparticular stoichiometric ratio for the preparation of a polyoxoanionmay correspond to the above identified species, the actual speciespresent in either the crystalline form or in situ, may differ from thoseidentified above. Rather, the crystals, or in situ preparation, arelikely to contain a mixture of many different species of thepolyoxoanion. Thus, although sometimes not immediately isolable, allspecies formed when the polyoxoanions described above are prepared andused are intended to be within the scope of this invention.

It is also intended to be within the scope of this invention to use amixture of polyoxoanions as the polyoxoanion component of the inventivecatalyst system. In certain cases, the mixture of polyoxoanions mayproduce catalytic activity possessed by none of the mixture's individualpolyoxoanion components. It will also be recognized, by one skilled inthe art, that just as certain mixtures of polyoxoanions result inimproved results, there are other mixtures which detract from thecatalyst activity of the individual components.

Although the above generic and sub-generic descriptions cover all of thespecies which are useful in this catalyst system, several broadersubgenera have been identified which exhibit unexpected catalystactivity. For example, catalyst systems comprising molybdenum-freepolyoxoanions, or vanadium-free polyoxoanions, have been demonstrated toprovide the necessary catalyst activity to obtain improved conversionsand selectivities.

Counteractions for the polyoxoanions can be protons, alkali metalcations, alkaline earth cations, transition metal cations, includingcations of Pd, Cu, Co and Mn, and organic cations. Preferred cations foruse in the present catalyst system include protons, Cu, Na, K and Li.

The amount of polyoxoanion used has to be large enough so that thereoxidation of Pd° to Pd⁺² is not rate limiting for the overalloxidation reaction. Yet, the amounts of polyoxoanion must be low enoughto be cost effective while simultaneously giving reaction solutions ofreasonable viscosity.

(2) Palladium Component

Any palladium containing material, or mixtures thereof, which aresuitable for catalytic oxidation of olefins can be used in the catalystsystem of the present invention. Finely divided palladium metal powder,palladium metal, and essentially chloride-free palladium compounds areall useful in the present invention, either individually or incombination. The preferred compounds are palladium trifluoroacetate,Pd(CF₃ COO)₂ ; palladium acetate, Pd(CH₃ COO)₂ ; palladium sulfate,PdSO₄ ; and palladium nitrate, Pd(NO₃)₂. Although chloride-freepalladium salts are preferred, it is intended to be within the scope ofthis invention to use palladium chloride.

(3) Redox Active Metal Component

Any metal component which is capable of undergoing a change in valenceunder the reaction conditions of olefin oxidation, or mixtures thereof,can be used in the catalyst system of the present invention. Thecounter-anion to this redox active metal should not contain chlorides.Preferred redox active metal components include cupric (cuprous)sulfate, CuSO₄ ; cupric acetate, Cu(CH₃ COO)₂ ; cupric nitrate Cu(NO₃)₂,and ferrous (or ferric) acetate, Fe(CH₃ COO)₂ ;, ferrous (or ferric)sulfate, FeSO₄.

(4) Ligands

Since the ligand compounds serve a number of functions there are alimited number of them. A class of compounds which are useful in theinstant invention are the family of nitriles (RC.tbd.N), includingbenzonitrile. The preferred ligand is acetonitrile.

C. Olefin Oxidation Process (1) Substrates

The olefinic hydrocarbon reactant, or substrate, which is oxidizedaccording to the process of the instant invention is basically anyhydrocarbon containing at least one carbon-carbon double bond, ormixtures of such hydrocarbons. The olefinic hydrocarbon, which containsat least two carbon atoms per molecule, can be either substituted (e.g.,4-methyl, 1-pentene) or unsubstituted (e.g., 1-pentene), and eithercyclic (e.g., cyclohexene) or acyclic (e.g., 2-hexene). If the olefinichydrocarbon is acyclic, the carbon-carbon double bond can be eitherterminal (so-called alpha-olefins) or non-terminal (so-called internalolefins). If the olefinic hydrocarbon contains more than onecarbon-carbon double bond, the double bonds can be conjugated orunconjugated. No particular upper limit applies to the carbon number ofthe olefinic hydrocarbon. However, a practical limitation is that boththe reactivity of the hydrocarbon and the selectivity to the carbonylcompound(s), in general, tend to decrease with increasing carbon number.The decrease in selectivity is partially due to the increasedisomerization tendency of higher olefins. One feature of the presentinvention is that the decrease in reactivity and selectivity resultingfrom increasing the carbon number is much less dramatic than is found inprior art. This is achieved through a delicate balance of theconcentration and type of redox active metal and (or) ligand andstirring efficiency (reactor design). Thus oxidation of higher olefinsappears commercially practical.

Olefinic hydrocarbons exhibit different reactivities depending on theirstructure. As a general rule, acyclic terminal olefins react faster thanacyclic internal olefins, acyclic olefins react faster than cyclicolefins, and unsubstituted olefins react faster than substitutedolefins. Exceptions to that rule which have been observed under theconditions of the present invention are: 2-butene reacts faster than1-butene; cyclohexene reacts faster than 1-hexene. Preferred olefinichydrocarbons are therefore unsubstituted terminal mono olefins, such asethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene,1-octadecene, 1-eicosene and higher terminal mono olefins, unsubstitutedbeta-olefins, such as 2-butene, 2-pentene, 2-hexene, 2-octene, andhigher beta-olefins, and cyclic olefins, such as cyclohexene, 3-methyl1-cyclohexene and many others.

(2) Solvent

Since the solvent is present in large excess compared to the catalystcomponents, one must select a solvent that does not affect the catalystsystem adversely. Solvents of choice are water or water/ligand mixtures.Other solvents potentially can be used if the catalyst components remainactive.

(3) Acid Component

pH or acidity can be adjusted by various proton sources, such as an acidform of a polyoxoanion or an inorganic acid like HBF₄, HNO₃, or H₂ SO₄.In some cases an organic acid like acetic acid may be acceptable. Apreferred acid is sulfuric acid.

(4) Oxygen

Depending on the process one can use either air or oxygen. Other sourcesof oxygen are acceptable but would be less economical. Similarly otheroxidants would be acceptable but are anticipated to be less economical.

(5) Stirring Speed

The product distribution in an oxidation can be highly dependent on thestirring speed in the reactor. Since the reactions tend to bemultiphase, the rate limiting step can be the supply of a reagent to thecatalyst (e.g, oxygen or olefin). Increasing the stirring speed canincrease the mass transport of the reactants to the catalyst and/or themass transport of products from the catalyst into the bulk solution.Depending on the intermediate species in the rate determining stepsleading to the various products, the ratio of these products can changeas a function of the mass transport. In the catalyst systems of theinstant invention it has been observed in many cases that increasing thestirring speed dramatically increases the oxidation rate over theisomerization rate. The oxidation rate is increased by the higher oxygenconcentration while the isomerization appears to be independent of theoxygen and the olefin concentration.

(6) Process Conditions

The optimum temperature for the olefin oxidation reaction can varydepending upon the individual olefin substrate. Low molecular weightliquid olefins become increasingly volatile at higher temperatures. Highreaction temperatures may not be desired in view of the increasedvolatility. The reaction temperature is typically between 20° C. and175° C., preferably 65° C. to 90° C. At lower temperatures the rate ofoxidation becomes too slow and at higher temperatures overoxidation canbe a problem. In the case of nitriles, hydrolysis to amides and acidscan be problematic above 85° C.

The operating pressure for the oxidation reaction is typically between0-200 psig. At lower pressures the rate of oxidation can be too slowwhile at higher pressures the risks of overoxidation and explosionincrease.

The pH of the liquid phase is maintained between 0 and 7, preferablybetween 1 and 3, by the addition of appropriate amounts of H₂ SO₄. Bothat lower and at higher pH the polyoxoanions tend to decompose.

The ratio of Pd/polyoxoanion/redox active metal varies from 1/0.5/0.2 to1/50/500 but preferably lies around 1/5/10.

The amount of ligand present can vary from 1 mole/mole of palladium(and) or redox active metal to where it is the main component of thesolvent. The optimum varies for different olefins and differentheteropolyoxoanion systems.

Reaction times vary from a few minutes to 48 hours. Short reaction timescan lead to heat management problems while long reaction times lead toeconomically unattractive large reactor sizes.

D. Working Examples

The examples set forth below fall into two major categories. ExamplesI-XXVI illustrate some of the methods used to prepare the polyoxoanioncomponents of the instant invention. In some cases the preparations wereespecially developed for this invention and in other cases the methodsused are analogous to methods of preparation published in the openliterature (R. Massart et al., Inorg. Chem., 16, 2916 (1977); A.Bjornberg, Acta Cryst., B35, 1995 (1979); Misono et al., Bull. Chem.Soc. Jap., 55, 400 (1982); R. Strandberg, Acta Chem. Scand., 27, 1004(1973); B. Dawson, Acta Cryst., 6, 113-126 (1953); M. Droege, Ph.D.Dissertation, University of Oregon, (1984); R. Constant et al., J. Chem.Res., p. 222(s) and p. 2601-2617(m) (1977)). Wherever possible, thesynthesis of the polyoxoanion was done in the absence of chloride ions.In some cases, chloride ions were present in order to form and (or)crystallize the desired structure. In these cases, it was shown byanalysis that only trace amounts of chloride were present.

The second category, Examples XXVII-XLII, pertains to the oxidationprocess itself.

EXAMPLE I: K₉ PMo₆ V₆ O₄₀

The preparation of this heteropolyoxoanion is based on the one describedin Smith, Pope "Inorganic Chemistry", Volume 12, pages 331 (1973).

In a first flask, 73.2 grams of sodium meta vanadate (NaVO₃) weredissolved in 380 ml of distilled water which had been heated to 90° C.80.7 grams of sodium molybdate (Na₂ MoO₄.2H₂ O) were added to 120 ml ofdistilled water contained in a second, round bottom flask. Thismolybdate solution was heated to 90° C. and stirred. The vanadatesolution in the first flask was added to the round bottom flask whichwas then fitted with a reflux condenser. The solution in the roundbottom flask turned yellow-orange.

50 ml of 85% phosphoric acid (H₃ PO₄) were added dropwise to theyellow-orange solution which turned it very dark. The solution washeated to 95° C. for 1 hour and then filtered through Celite®(Johns-Manville Corp., Denver, Colo. The Celite® was washed with a smallamount of cold water.

Approximately 80 grams of potassium sulfate (K₂ SO₄) were added to thefiltrate which had been cooled to room temperature. The solution wasstirred for one to one and one-half hours. The precipitate which hadformed was collected and dried in a vacuum oven. The solid wasrecrystallized from 120 ml of 0.25M sulfuric acid (H₂ SO₄). The crystalswere dried in a vacuum oven.

The potassium salt K₉ PMo₆ V₆ O₄₀ was used to prepare a lithium salt Li₉PMo₆ V₆ O₄₀ by ion-exchange chromatography. The acid form of anAmberlyst® (Rohm & Haas, Philadelphia, Pa.) ion-exchange resin wasexchanged to the Li⁺ form by eluting with 1M lithium hydroxide (LiOH).After washing the column free of excess hydroxide the acid form of PMo₆V₆ O₄₀ ⁻⁹ was slowly eluted down the column with water. Removal of wateryielded the more soluble lithium salt of PMo₆ V₆ O₄₀ ⁻⁹.

EXAMPLE II: Na₁₁ PMo₄ V₈ O₄₀

The preparation of this heteropolyoxoanion is based on the one describedin S. F. Davison's Ph.D. Dissertation, University of Sheffield (1982).

5.7 grams sodium phosphate (Na₃ PO₄.12H₂ O), 8.64 grams molybdenumtrioxide (MoO₃), 14.74 grams of vanadium pentoxide (V₂ O₅) and 2.41grams of sodium carbonate (Na₂ CO₃) were added to 75 ml of distilledwater on a one neck, round bottom flask. The solution was heated toreflux and kept there for one hour. The resulting red solution wasfiltered through Celite®. The filtrate volume was reduced on a rotovapand the sodium salt Na₁₁ PMo₄ V₈ O₄₀ was crystallized from the remainingliquid by cooling.

EXAMPLE III: Na₇ PMo₈ V₄ O₄₀

The preparation of this heteropolyoxoanion is based on the one describedin S. F. Davison's Ph.D. dissertation, University of Sheffield (1982).5.7 grams sodium phosphate (Na₃ PO₄ ·12H₂ O), 17.25 grams molybdenumoxide (MoO₃), 6.3 grams vanadium pentoxide (V₂ O₅) and 2.41 grams sodiumcarbonate (Na₂ CO₃) were added to 75 ml of water in a one neck, roundbottom flask. The solution was heated to reflux and refluxed for onehour. The resulting red solution was filtered through Celite®. Thefiltrate volume was reduced on a rotary evaporation and the sodium saltNa₇ PMo₈ V₄ O₄₀ was crystallized from the remaining liquid by cooling.

EXAMPLE IV: P₂₁ W₁₂ Mo₅ VO₆₂ ⁻⁷ ##STR10## a. K₆ [α,β-P₂ W₁₈ O₆₂ ]

The preparation of this polyoxoanion is based upon the one described inB. Dawson, Acta Cryst. 6, 113-126 (1953). 400 grams of sodium tungstate(Na₂ WO₄ ·2H₂ O) was added to 700 ml of boiling distilled water. 85%phosphoric acid (H₃ PO₄) was added dropwise to the boiling solution. Thesolution turned light green during the dropwise addition. The entiremixture was refluxed for approximately eight hours. After cooling toroom temperature, 100 grams of potassium sulfate (K₂ SO₄) was added. Thesolution was left to crystallize for several hours. The solid, agreen-yellow precipitate of the formula K₆ [α,β-P₂ W₁₈ O₆₂ ], wascollected. The filtrate was discarded.

b. K₆ [α-P₂ W₁₈ O₆₂ ]

The preparation of this polyoxoanion is based on the one described in M.Droege, Ph.D. Dissertation, University of Oregon (1984). 160 grams ofthe potassium salt K₆ [α,β-P₂ W₁₈ O₆₂ ] was dissolved in 500 ml ofdistilled water contained in a two-liter flask. The solution was heatedgently to dissolve all of the solids. After all of the solids weredissolved, the solution was cooled to room temperature. A 10% potassiumbicarbonate (KHCO₃) solution was added via an addition funnel. After theaddition of 150 ml of potassium bicarbonate a precipitate formed. Uponfurther addition of 450 ml the solid dissolved and the solution wascolorless. Next, 320 ml of 6N sulfuric acid was added in 10 ml aliquots,to regenerate the anion α-P₂ W₁₈ O₆₂ ⁻⁶. After all of the sulfuric acidhad been added, the solution was yellow-green with slight precipitation.The solution was filtered through Celite®. 50 grams of potassium sulfatewere added to the filtrate and a precipitate appeared immediately. Theprecipitate K₆ [α-P₂ W₁₈ O₆₂ ] was collected, washed and dried in anoven.

c. K₁₂ H₆ P₂ W₁₂ O₅₀

The preparation of this polyoxoanion is based on the one described in R.Contant et al., J.Chem.Res., 222(s), 23601-2617(m) (1977). 80 grams ofthe potassium salt K₆ [α-P₂ W₁₈ O₆₂ ] were dissolved in 500 ml of waterand 200 ml of a 2M tris [(HOCH₂)₃ CNH₂ ] buffer solution and left tostir for thirty minutes. About 40 grams of potassium sulfate and 200 mlof 2M potassium carbonate (K₂ CO₃) were added to the solution and thewhite precipitate K₁₂ H₆ P₂ W₁₂ O₅₀ appeared. The solution was cooled to10° C. and filtered. The product was washed with saturated potassiumsulfate and then dried in a vacuum oven.

d. K₆ P₂ W₁₂ Mo₆ O₆₂

The preparation of this polyoxoanion is based on the one described in R.Massart et al., Inorg.Chem., 16, 2916 (1974). About 75 grams of thepotassium salt K₁₂ H₆ P₂ W₁₂ O₅₀ was added to 75 ml of 1M lithiumchloride (LiCl) and was acidified to pH 2 with 1N hydrochloric acid.Additional lithium chloride was added, but the potassium salt was stillsomewhat insoluble. Next 15.7 grams of lithium molybdate (Li₂ MoO₄) wasadded to the solution which then became bright yellow and almost clear.The solution was again acidified with 1N hydrochloric acid to pH 4.5.Precipitation occurred upon cooling. The precipitate, potassium andlithium salts of the anion P₂ W₁₂ Mo₆ O₆₂ ⁻⁶, was collected, washed anddried. The precipitate was recrystallized from 100 ml of 0.1N sulfuricacid to remove traces of chloride and to obtain the potassium from K₆ P₂W₁₂ Mo₆ O₆₂. In its hydrated form, the salt has the formula K₆ P₂ W₁₂Mo₆ O₆₂ ·14H₂ O.

e. K₁₀ P₂ W₁₂ Mo₅ O₆₁ ·20H₂ O, K₇ P₂ W₁₂ Mo₅ VO₆₂

40 grams of the potassium salt K₆ P₂ W₁₂ Mo₆ O₆₂ ·14H₂ O was dissolvedin 140 ml of water and then was treated with 80 ml of 1M potassiumbicarbonate (KHCO₃). A white-yellow precipitate was collected andcrystallized from 30 ml of hot water. The white precipitate has thegeneral formula K₁₀ P₂ W₁₂ Mo₅ O₆₁ ·20H₂ O.

10 grams of the potassium hydrate K₁₀ P₂ W₁₂ Mo₅ O₆₁ ·20H₂ O weredissolved in 40 ml of distilled water and was vigorously stirred. 2.2 mlof 1M lithium vanadate (LiVO₃), 10 ml of 1M hydrochloric acid and 2.7 mlof concentrated 12M hydrochloric acid were added consecutively to thesolution. Then, 11 grams of potassium chloride were added. A brightorange precipitate K₇ P₂ W₁₂ Mo₅ VO₆₂ was collected and air dried.

EXAMPLE V. H₇ P₂ W₂ VO.sub.β ##STR11## a. Na₁₂ P₂ W₁₅ O₅₆

The preparation of this polyoxoanion is based on the one described in M.Droege Ph.D. Dissertation, University of Oregon (1984). 80 grams of thepotassium salt K₆ [α-P₂ W₁₈ O₆₂ ] were dissolved in 267 ml of water.Next, 107 grams of sodium perchlorate (NaClO₄) were added. Thelight-green solution was stirred for 2 hours; the insoluble precipitatepotassium perchlorate (KClO₄) was filtered off. About 200 ml of 1Msodium carbonate (Na₂ CO₃) was added to the filtrate to obtain a pH of9. The solution was essentially colorless at this point. A white solid,Na₁₂ P₂ W₁₅ O₅₆, precipitated and was collected. The precipitate waswashed with sodium chloride (NaCl) solution, ethanol and diethyl ether[(CH₃ CH₂)₂ O], and then was dried for eight hours at 60° C.

b. P₂ W₁₅ Mo₂ O₆₁ ⁻¹⁰

To 150 ml of an aqueous solution containing 0.013 moles of sodiummolybdate hydrate (Na₂ MoO₄ ·2H₂ O) and 11 ml of 1M HCl was added 10grams of the potassium salt K₁₂ P₂ W₁₅ O₅₆. The solution was stirreduntil clear. 1M HCl was then added dropwise until the pH was 6-6.5. Then7 grams of potassium chloride KCl was added. A white precipitate K₁₀ P₂W₁₅ Mo₂ O₆₁ resulted and was filtered, washed and dried.

c. P₂ W₁₅ Mo₂ VO₆₂ ⁻⁷

13.5 grams of the potassium salt K₁₀ P₂ W₁₅ Mo₂ O₆₁ was dissolved in 50ml of water. The solution was vigorously stirred while in the followingorder 0.35 g of lithium vanadate (LiVO₃), 25 ml of 1M hydrochloric acidand about 4 ml of concentrated hydrochloric acid were added. Thesolution turned yellow with the addition of lithium vanadate. Potassiumchloride was added to cause precipitation of the potassium salt K₇ P₂W₁₅ Mo₂ VO₆₂.

EXAMPLE VI: K₈ Mo₄ V₈ O₃₆

The preparation of this isopolyoxoanion is based on the preparationdescribed by A. Bjornberg, Acta Cryst. 1979, B35, p. 1989. 14.40 gramsof molybdenum trioxide (MoO₃) was added to 200 ml of 0.5M KOH. A whitesuspension was obtained. 23.40 grams of ammonium meta vanadate (NH₄ VO₃)was mixed with 240 ml of distilled water. The above two slurries weremixed. While stirring vigorously 50 ml of 2M H₂ SO₄ was added until thepH was ˜1.5-2.0. A red-orange color formed as the solids reacted anddissolved in the solution. Next, 35 grams of potassium sulfate (K₂ SO₄)was added and the volume of the solution was reduced by two-thirds bythe removal of water under vacuum. The resulting solution was left in arefrigerator overnight to crystallize. The salt K₈ Mo₄ V₈ O₃₆ wasfiltered and dried in a vacuum oven at 40° C.

EXAMPLE VII: K₅ Mo₃ V₃ O₁₉

20.0 grams of sodium molybdate (Na₂ MoO₄ ·2H₂ O) and 10.08 grams ofsodium vanadate (NaVO₃) were added to an acetate buffer of pH 6.4.Potassium chloride was added to precipitate the isopolyoxoanion K₅ Mo₃V₃ O₁₉ which was filtered, washed, and dried.

EXAMPLE VIII: Na₆ Mo₆ V₂ O₂₆ ·16H₂ O

This preparation was based on the one described in Bjornberg, ActaCryst. 1979, B35, p. 1995. 6.1 grams of sodium vanadate (NaVO₃) wasdissolved in 150 ml of hot distilled water. In a second flask, 36.3grams of sodium molybdate (Na₂ MoO₄ ·2H₂ O) was dissolved in 150 ml ofhot distilled water. The two solutions were mixed. 66.65 ml of 3M HClwas added dropwise while the solution was vigorously stirred. Then 30grams of NaCl was added to the solution. A solid Na₆ Mo₆ V₂ O₂₆ ·16H₂ Oformed and was filtered and dried.

EXAMPLE IX: [Mo₄ V₈ O₃₆ ]⁻⁸

This is an in situ preparation. Two separate solutions of 2.24 grams ofsodium molybdate (Na₂ MoO₄ ·2H₂ 0) and 2.25 grams of sodium metavanadate (NaVO₃) were mixed and diluted to 50 ml with distilled water. 5ml of the above solution were pipetted into 11.5 ml of reaction solventcontaining 1.73 mmole of sulfuric acid (H₂ SO₄). The pH of the solutionwas 1.6. The reaction solution had turned orange because theisopolyoxoanion [Mo₄ V₈ O₃₆ ]⁻⁶ had formed.

EXAMPLE X: [Mo₆ V₆ O₃₆ ]⁻⁶

This is a simplex preparation, also known as in situ. 0.354 grams ofsodium vanadate (NaVO₃) were dissolved in 30 ml of distilled water.Next, 0.702 grams of sodium molybdate (Na₂ MoO₄ ·2H₂ O) was added. ThepH of the resulting solution was adjusted to 1.6 with concentrated H₂SO₄. The final volume was adjusted to 36 ml by addition of distilledwater. The polyoxoanion [Mo₆ V₆ O₃₆ ]⁻⁶ was present in the aqueoussolution.

EXAMPLE XI: [Mo₈ V₄ O₃₆ ]⁻⁴

0.9368 grams of sodium molybdate (Na₂ MoO₄ ·2H₂ O) and 0.2361 grams ofsodium vanadate (NaVO₃) were dissolved in 36 ml of distilled water. ThepH of the solution was adjusted to 1.6 by the addition of concentratedH₂ SO₄. The polyoxoanion [Mo₈ V₄ O₃₆ ]⁻⁴ was present in solution and wasused in the olefin oxidation reactions.

EXAMPLE XII: [W₂ Mo₆ V₄ O₃₆ ]⁻⁴

This isopolyoxoanion was made by an in situ method. 1.52 grams of sodiumtungstate (Na₂ WO₄ ·2H₂ O) was dissolved in 10 ml of distilled water.1.126 grams of sodium meta vanadate (NaVO₃) was dissolved in another 10ml of hot distilled water. 3.35 grams of sodium molybdate (Na₂ MoO₄ ·2H₂O) was dissolved in yet a third 10 ml of distilled water. The threesolutions were combined and diluted to 50 ml with additional distilledwater. The solution was acidified to pH 2 with 0.78 ml of 5N sulfuricacid. This solution now contained [W₂ Mo₆ V₄ O₃₆ ]⁻⁴ and was used in theolefin oxidation reactions.

EXAMPLE XIII: [W₆ Mo₂ V₄ O₃₆ ]⁻⁴

This is an in situ preparation. Three separate solutions containing 4.57grams of sodium tungstate (Na₂ WO₄ ·2H₂ O), 1.12 grams of sodiummolybdate (Na₂ MoO₄ ·2H₂ O) and 1.13 grams of sodium meta vanadate(NaVO₃), respectively, were mixed and diluted to 50 ml with distilledwater. The isopolyoxoanion [W₆ Mo₂ V₄ O₃₆ ]⁻⁴ was formed by pipetting5.0 ml of the above mixture into 11.5 ml of reaction solvent containing2.60 mmole of sulfuric acid. The pH was maintained at ˜1.6.

EXAMPLE XIV: [W₇ Mo₃ V₂ O₃₆ ]⁻²

1.13 grams of sodium tungstate (Na₂ WO₄ ·2H₂ O), 0.408 grams of sodiummolybdate (Na₂ MoO₄ ·2H₂ 0) and 0.085 grams of sodium vanadate (NaVO₃)were added to 36 ml of distilled water. The pH of the resulting solutionwas adjusted to 1.6 with concentrated sulfuric acid. The isopolyoxoanion[W₇ Mo₃ V₂ O₃₆ ]⁻² was present in the solution.

EXAMPLE XV: [W₆ V₆ O₃₆ ]⁻⁶

4.57 grams of sodium tungstate (Na₂ WO₄ ·2H₂ O) was dissolved in 20 mlof distilled water. 1.69 grams of sodium vanadate (NaVO₃) was dissolvedin 20 ml of hot distilled water. The two solutions were combined anddiluted to 50 ml. The isopolyoxoanion [W₆ V₆ O₃₆ ]⁻⁶ was formed bypipetting 5.0 ml of the above solution into 11.5 ml of reaction solventcontaining 3.20 mmole of sulfuric acid (H₂ SO₄). The pH was ˜1.6.

EXAMPLE XVI: Na₆ P₂ Mo₁₈ O₆₂

This preparation is based on the one described in Rene Massart et. al.,Inorganic Chemistry, 16, 2916 (1977).

18 grams sodium monohydrogen phosphate as the hydrate (Na₂ HPO₄ ·12H₂ O)was dissolved in a mixture of 73 ml of 11.7N perchloric acid (HClO₄) and20 ml of water. A solution of 108 grams of sodium molybdate dihydrate(Na₂ MoO₄ ·2H₂ O) in 200 ml of water was added dropwise to the firstsolution. A yellow precipitate formed. Heating the solution changed thecolor to orange. The solid Na₆ P₂ Mo₁₈ O₆₂ crystallized and wasseparated, washed, and dried.

EXAMPLE XVII: K₆ P₂ W₁₂ Mo₆ O₆₂

See Example IV-a,b,c,d for the preparation of K₆ P₂ W₁₂ Mo₆ O₆₂.

EXAMPLE XVIII: Na₃ PMo₆ W₆ O₄₀, H₃ PMo₆ W₆ O₄₀, Li₃ PMo₆ W₆ O₄₀

This preparation is based in the one described in Misono et al., Bull.Chem. Soc. Jap., 55, 400 (1982). 45 grams of sodium tungstate dihydrate(Na₂ WO₄ ·2H₂ O), 33 grams of sodium molybdate dihydrate (Na₂ MoO₄ ·2H₂O) and 12.25 grams of sodium monohydrogen phosphate septa hydrate (Na₂HPO₄ ·12H₂ O) were dissolved in 200 ml of distilled water and thesolution was heated to 80° C. for three hours with stirring. Thesolution volume was reduced to about 50 ml by use of a rotaryevaporator. A white precipitate appeared. The precipitate wasredissolved by the addition of about 40 ml of water. A yellowprecipitate, the sodium salt Na₃ PMo₆ W₆ O₄₂, was formed when thesolution was acidified by the addition of 100 ml of 24% hydrochloricacid. The precipitate was collected, washed and dried in a vacuum oven.

The sodium salt solution was slowly eluted down a cation ion exchangecolumn which was in the H⁺ form. The water eluate was extracted withether. The ether was evaporated leaving H₃ PMo₆ W₆ O₄₀.

The acid form of an Amberlyst® resin was converted to the Li⁺ form bytreatment with lithium hydroxide (LiOH). The excess lithium hydroxidewas washed out. An aqueous solution of Na₃ PMo₆ W₆ O₄₀ was eluted slowlydown the column. The lithium salt was obtained by reducing the volume ofeluant which led to the crystallization of Li₃ PMo₆ W₆ O₄₀.

EXAMPLE XIX: H₆ P₂ Mo₅ O₂₃

The preparation is based on the one described in R. Strandberg, Acta.Chem. Scand., 27, 1004 (1973). 74 grams of sodium molybdate dihydrate(Na₂ MoO₄ ·2H₂ O) and 14.76 grams of sodium dihydrogenphosphate (NaH₂PO₄) were dissolved in 150 ml of distilled water. 31.5 ml of 11.7Mperchloric acid (HClO₄) were added to the solution. The resultingsolution was poured into a crystallizing dish, was covered and set asideuntil H₆ P₂ Mo₅ O₂₃ crystallized. The product was filtered and dried.

EXAMPLE XX: [Mo₆ W₆ O₄₁ ]⁻¹⁰

This isopolyoxoanion is prepared according to the simplex method, or insitu. 0.7026 g of sodium molybdate (Na₂ MoO₄ ·2H₂ O) and 0.9580 g ofsodium tungstate (Na₂ WO₄ ·2H₂ O) were dissolved in 36 ml of distilledwater. The pH was adjusted to 1.6 with concentrated sulfuric acid. Thespecies [Mo₆ W₆ O₃₆ ] is present in the resulting solution.

EXAMPLE XXI: H₉ PV₁₄ O₄₂, Na₉ PV₁₄ O₄₂

The preparation of these heteropolyoxoanions is based on the preparationdescribed by Kato N., et al., Inorg. Chem., 21, p. 240 (1982). 90 gramsof sodium vanadate (NaVO₃) were dissolved in about 500 ml of boilingdistilled water. As the solution cooled to room temperature, 25 ml of7.4M phosphoric acid (H₃ PO₄) was added dropwise. The pH was adjusted to1.7 with 100 ml of 3.4M nitric acid (HNO₃). A dark-brown-redprecipitate, the acid and sodium salts of PV₁₄ O₄₂ ⁻⁹, formed. Thesolution was left to cool to further crystallize the vanadium compounds.The crystals were filtered, washed and dried.

EXAMPLE XXII: PWV₁₁ O₄₀ ⁻¹⁴, PWV₁₂ O₄₁ ⁻¹¹

See Example XXIII below for their preparation.

EXAMPLE XXIII: K₅ H₄ PW₆ V₆ O₄₀

The preparation of this heteropolyoxoanion is based on the preparationdescribed in D. P. Smith's Ph.D. dissertation, Georgetown University(1975). In a three-neck, round bottom flask, 110 grams of sodiumtungstate (Na₂ WO₄ ·2H₂ O) was added to 120 ml of distilled water andthe solution was heated to 85° C. 73.2 grams of sodium vanadate (NaVO₃)was added to 380 ml of distilled water which had been preheated to 90°C. The two hot solutions were combined in the round bottom flask, andwere kept at 90° C. 50 ml of 85% phosphoric acid was added dropwise,turning the orange-gold solution to a black-red color. The solution wasmaintained at 95° C. for one hour.

The solution was then filtered through Celite® and the filtrate wasallowed to cool to room temperature. 27 grams of solid potassium nitrate(KNO₃) and then a solution of 68 grams of potassium nitrate in 200 ml ofdistilled water were added to the filtrate. The solution was left foreight hours with continuous stirring. A yellow-orange precipitate, amixture of acid and potassium salts of the anion PW₆ V₆ O₄₀ ⁻⁹ formed.The solids were filtered, washed, and recrystallized from a weaklyacidic solution to form yellow and red crystals. A second batch ofyellow crystals were obtained from the filtrate. Analysis of the secondbath indicated anions of the form PWV₁₁ O₄₀ ⁻¹⁴ and PWV₁₂ O₄₁ ⁻¹¹.

EXAMPLE XXIV: Na₇ PMo₈ V₄ O₄₀

The preparation of this polyoxoanion is based on the preparationdescribed in S. F. Davidson's Ph.D. Dissertation, University ofSheffield (1982). 5.7 grams of sodium phosphate dodecahydrate (Na₃ PO₄·12H₂ O), 17.25 grams of molybdenum trioxide (MoO₃) and 6.3 grams ofvanadium pentoxide (V₂ O₅) and 2.41 grams of Na₂ CO₃ were dissolved in75 ml of water. The solution was heated to 90° C. and kept there for onehour. The precipitate, Na₇ PMo₈ V₄ O₄₀, was filtered, washed and dried.The filtrate was cooled and its volume reduced by a rotary evaporator toobtain a second batch of crystals.

EXAMPLE XXV: Na₁₂ P₂ W₁₂ V₆ O₆₂

See Example IVa, b, and c for the preparation of the sodium salt Na₁₂ H₆P₂ W₁₂ O₅₀.40 grams of the sodium salt were dissolved in 500 ml of 1MLiCl acidified to pH 2. A solution of 7.2 grams of sodium vanadate(NaVO₃) in 100 ml of water was added to the first solution, and the pHwas adjusted to 5.5 with the addition of 1M HCl. A precipitate Na₁₂ P₂W₁₂ V₆ O₆₂ was filtered, washed and dried. A second batch K₁₂ P₂ W₁₂ V₆O₆₂ was obtained from the filtrate by the addition of potassiumchloride.

EXAMPLE XXVI: K₆ H₃ P₂ W₁₅ V₃ O₆₂

50.0 grams of sodium vanadate (NaVO₃) were dissolved in 600 ml hotdistilled water and then the solution was cooled to room temperature.The solution was acidified to pH 1.5 by the addition of 6.7 ml 12M HCl.The solution turned yellow. To the now vigorously stirred solution wasslowly added 57.1 grams of Na₁₂ P₂ W₁₅ O₅₆ ·18H₂ O (see Example Va),resulting in a cherry red solution. 3 ml of 12M HCl were added to alterpH to 1.5. Next, 45 grams of potassium chloride were added. Aprecipitate, K₆ H₃ P₂ W₁₅ V₃ O₆₂, formed. It was filtered andrecrystallized from water of pH 1.5, and then dried to give the finalproduct.

In all the runs that are described in the following examples XXVII-XLII,the reaction vessel utilized was either (a) an 80 ml Fischer-Porter®(Fischer-Porter Co., Warminster, Pa.) bottle having a magnetic stirrercapable of 250 rpm (hereinafter referred to as R1), (b) an 80 mlFischer-Porter® bottle with a motor driven titanium paddle stirrer (1750rpm) (hereinafter referred to as R2), or (c) a 100 ml Fluitron SS316reactor (5000 psi rating) with a conventional stirrer (2500 rpm maximum)(hereinafter referred to as R3). The observed relative oxidation rates,because of increased mass transport of oxygen and (or) olefin, increasefrom 1 to 4-6 to 20-40 in going from R1 to R2 to R3.

R1's were fitted with a pressure gage, oxygen inlet line, vent line, anda liquid injection port through which liquid (e.g., olefin) could beinjected at any desired operating temperature and pressure. Each R1 useda 3" long, 11/2" diameter Teflon® (DuPont Co., Wilmington, Del.) coatedstirring bar. The oxygen lines to the reactors were fitted with filtersand check valves. The R1's were heated in a glycol bath whosetemperature was controlled by a I² R Thermo-Watch. Each bath wasprotected from inadvertent overheating by an I² R Over-Temp Probe.

R2's were outfitted in a similar fashion as the R1's, the majordifference being the mode of stirring, i.e., the motor driven two bladepaddle stirrer. Both the stirrer shaft and paddle were made of titaniumso that comparison runs using corrosive concentrations of chloride couldbe carried out.

R3 was a 100 ml reactor manufactured by Fluitron Inc. of Warminster, Pa.The double disk six pitched blade stirrer was originally designed tocirculate the catalyst solution out of and into the reactor so that thereactor need not be depressurized for sampling. R3 was heated by anelectrical heater. The temperature was monitored by a thermocouple. Thetemperature was set using a RI Instruments controller and was monitoredon an Analog Devices Digital Thermometer. A Watlow over-heat monitor wasused to shut off the whole system. Representative samples could be takenusing a pressure syringe while R3 was in full operation.

All reactors were first loaded with the solvent followed by addition ofthe various catalyst components. The reactor was sealed andpressurized/depressurized at least four times with oxygen. The finalpressure was left at 80 psig. The reactor was then heated to thereaction temperature. The olefin was injected using a pressure syringewithout the need for depressurizing. Oxygen could be supplied byrepressurizing as the pressure fell or by leaving the oxygen supply lineopen to a constant pressure source of the gas.

In R1 and R2 oxidation runs, uniform samples could not be obtainedduring a run. In R3 reactions, uniform samples could be obtained as afunction of time.

After the desired reaction time, the reactors were quenched to roomtemperature and were depressurized. Injection of the water phase on agas chromatograph column showed whether some very polar compounds hadformed, e.g., acids. The reaction was then neutralized, extracted withmethylene chloride, and the methylene chloride solution was alsoanalyzed by GC.

In the following examples, "conversion" is defined as the moles ofolefin reacted per mole of olefin fed; "selectivity" is defined as themoles of ketone produced per mole of olefin reacted; "yield" is definedas the product of selectivity and conversion; and "turnover per Pol" isdefined as the moles of ketone produced per mole of Pd present in thesystem.

EXAMPLE XXVII

A series of 1-hexene oxidations were carried out in the presence of 15ml distilled water, 1.5 ml 1N H₂ SO₄, 625 mg of a polyoxoanion and 1:5molar ratio of Pd(CF₃ COO)₂ :polyoxoanion. An identical series ofcomparison oxidations were done havving a 1:5:10 molar ratio of Pd(CF₃COO)₂ :polyoxoanion:CuSO₄ 2H₂ O. All reactions were carried out with 2ml of olefin in R1 according to the above-described general procedure.The reaction conditions were 85° C. and 80 psig O₂ for 8 hours. Theresults are compiled in Table 1.

These runs demonstrate that the addition of a redox active metal canimprove conversion and (or) selectivity.

                                      TABLE 1                                     __________________________________________________________________________                            CuSO.sub.4                                                                        Hexene                                                                              Selectivity                                          Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         [mol]                                                                             Conversion                                                                          to 2-Hexanone                                                                         Turnovers                           Polyoxanion                                                                            [mol]* × 10.sup.3                                                               [mol] × 10.sup.2                                                               × 10.sup.2                                                                  mol % mol %   per Pd                              __________________________________________________________________________    P.sub.2 W.sub.15 V.sub.3 O.sub.62.sup.-9                                               1.60    0.80   --  30.8  76.9    143                                 "        1.60    0.80   1.58                                                                              35.9  99.1    214                                 PMo.sub.6 V.sub.6 O.sub.40.sup.-9                                                      3.54    1.77   --  53.7  90.8    131                                 "        3.54    1.77   3.53                                                                              73.7  95.0    189                                 P.sub.2 W.sub.12 Mo.sub.6 O.sub.62.sup.-6                                              1.60    0.80   --  3.9   35.5    8                                   "        1.60    0.80   1.60                                                                              10.6  60.5    38                                  Mo.sub.6 V.sub.6 O.sub.36.sup.-6                                                       3.66    1.83   --  70.0  94.5    198                                 "        3.66    1.83   3.67                                                                              85.5  90.0    172                                 Mo.sub.4 V.sub.8 O.sub.36.sup.-8                                                       2.79    1.39   --  25.6  86.0    77                                  "        2.79    1.39   2.79                                                                              47.4  89.7    150                                 W.sub.6 Mo.sub.2 V.sub.4.sup.-4                                                        2.79    1.39   --  14.0  72.8    36                                  "        2.79    1.39   2.79                                                                              43.4  84.7    126                                 __________________________________________________________________________     *[mol] represents mole per liter.                                        

EXAMPLE XXVIII

A series of 1-hexene oxidations were carried out in the presence of 16.5mls of aqueous solution adjusted to pH 1.6 with concentrated sulfuricacid. The solutions had a 1:5:10 molar ratio of Pd(CF₃ COO)₂ :POA:CuSO₄5H₂ O. The reactions were carried out with 2 ml of the olefin in R1according to the general procedure. The reaction conditions were 85° C.and 80 psig O₂ for 8 hours. The results are compiled in Table 2.

These runs demonstrate that oxidations using ispolyoxoanions and a redoxactive metal give high conversions of olefin, with high selectivity toproduct, with highest observed turnovers on palladium.

                                      TABLE 2                                     __________________________________________________________________________                            CuSO.sub.4                                                                        Hexene                                                                              Selectivity                                          Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         [mol]                                                                             Conversion                                                                          to 2 Hexanone                                                                         Turnovers                           Polyoxoanion                                                                           [mol] × 10.sup.3                                                                [mol] × 10.sup.2                                                               × 10.sup.2                                                                  mol % mol %   per Pd                              __________________________________________________________________________    [Mo.sub.4 V.sub.8 O.sub.36 ].sup.-8                                                    2.79    1.39   2.79                                                                              47.4  89.7    150                                 [Mo.sub.8 V.sub.4 O.sub.36 ].sup.-4                                                    2.79    1.39   2.79                                                                              76.0  86.8    222                                 [W.sub.2 Mo.sub.6 V.sub.4 O.sub.36 ].sup.-4                                            2.79    1.39   2.79                                                                              72.8  85.2    209                                 [W.sub.6 Mo.sub.2 V.sub.4 O.sub.36 ].sup.-4                                            2.79    1.39   2.79                                                                              43.4  84.7    126                                 [W.sub.6 V.sub.6 O.sub.36 ].sup.-6                                                     2.79    1.39   2.79                                                                              58.7  90.2    179                                 __________________________________________________________________________

EXAMPLE XXIX

A series of 1-hexene oxidations were carried out in the presence of 7.5ml distilled water, 7.5 ml CH₃ CN, 1.5 ml 1N H₂ SO₄, 625 mg of P₂ W₁₂Mo₆ O₆₂ ⁻⁶, 1:5 molar ratio of Pd(CF₃ COO)₂ :polyoxoanion, and a redoxactive metal. All reactions were carried out using R1 and 2 ml of olefinaccording to the general procedure. The reaction conditions were 85° C.and 80 psig O₂ for 8 hours. The results are compiled in Table 3.

These runs demonstrate that there exist a number of redox active metalswhich lead to increased oxidation rates, selectivities, and turnoversper palladium.

                                      TABLE 3                                     __________________________________________________________________________         Redox                                                                    Redox                                                                              Active                Hexene                                                                              Selectivity                                  Active                                                                             Metal(s)                                                                             Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         Conversion                                                                          to 2-Hexanone                                                                         Turnovers                            Metal(s)                                                                           [mol] × 10.sup.2                                                               [mol] × 10.sup.3                                                                [mol] × 10.sup.3                                                               mol % mol %   per Pd                               __________________________________________________________________________    --   --     1.60    8.0    25.9  18.1    28                                   CoSO.sub.4                                                                         1.60   1.60    8.0    21.7  18.0    23                                   MnSO.sub.4                                                                         1.60   1.60    8.0    26.5  28.7    45                                   FeSO.sub.4                                                                         1.67   1.60    8.0    91.8  24.1    132                                  CuSO.sub.4                                                                         1.60   1.60    8.0    97.5  30.0    173                                  __________________________________________________________________________

EXAMPLE XXX

A series of 1-hexene oxidations were carried out in the presence of 15ml distilled water, 1.5 ml 1N H₂ SO₄, 625 mg of polyoxoanion, and 1:5molar ratio of Pd(CF₃ COO)₂ :polyoxoanion. An identical series ofcomparison oxidations were done in the presence of 7.5 ml distilledwater, 7.5 ml acetonitrile (CH₃ CN), and 1.5 ml 1N H₂ SO₄. All reactionswere carried out with 2 ml of olefin in R1 according to the generalprocedure. The reaction conditions were 85° C. and 80 psig O₂ for 8hours. The results are compiled in Table 4.

These runs demonstrate that the addition of a ligand, in this caseacetonitrile, can improve conversion and oxidation turnovers perpalladium atom. Selectivities in this example are lower as a result ofthe higher conversions attained.

                                      TABLE 4                                     __________________________________________________________________________                                 Hexene                                                                              Selectivity                                         Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         CH.sub.3 CN                                                                        Conversion                                                                          to 2-Hexanone                                                                         Turnovers                          Polyoxoanion                                                                           [mol] × 10.sup.3                                                                [mol] × 10.sup.2                                                               + or -                                                                             mol % mol %   per Pd                             __________________________________________________________________________    P.sub.2 Mo.sub.18 O.sub.62.sup.-6                                                      2.13    1.07   -    17.5  48.6    38                                 "        2.13    1.07   +    48.5  43.8    95                                 PW.sub.6 V.sub.6 O.sub.40.sup.-9                                                       2.77    1.39   -    55.2  91.6    174                                "        2.77    1.39   +    95.9  71.5    236                                P.sub.2 W.sub.12 Mo.sub.6 O.sub.62.sup.-6                                              1.60    0.80   -    5.2   29.3    9                                  "        1.60    0.80   +    25.9  18.1    28                                 __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________                            CuSO.sub.4                                                                             Hexene                                                                              Selectivity                                     Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         [mol]                                                                             CH.sub.3 CN                                                                        Conversion                                                                          to 2-Hexanone                                                                         Turnovers                      Polyoxoanion                                                                           [mol] × 10.sup.3                                                                [mol] × 10.sup.2                                                               × 10.sup.2                                                                  + or -                                                                             mol % mol %   per Pd                         __________________________________________________________________________    PMo.sub.6 W.sub.6 O.sub.40.sup.-3                                                      2.53    1.27   --  -    4.2   9.1     1                              "        2.53    1.27   2.54                                                                              +    99.4  38.6    145                            P.sub.2 W.sub.12 Mo.sub.6 O.sub.62.sup.-6                                              1.60    0.80   --  -    5.2   29.3    9                              "        1.60    0.80   1.60                                                                              +    97.5  30.0    136                            P.sub.2 Mo.sub.18 O.sub.62.sup.-6                                                      2.13    1.07   --  -    17.5  48.6    38                             "        2.13    1.07   2.14                                                                              +    86.4  23.1    89                             P.sub.2 W.sub.12 Mo.sub.5 VO.sub.62.sup.-7                                             1.57    0.78   --  -    4.8   19.7    6                              "        1.57    0.78   1.56                                                                              +    12.2  31.3    23                             Mo.sub.6 V.sub.6 O.sub.36.sup.-6                                                       3.66    1.83   --  -    85.5  90.0    172                            "        3.66    1.83   3.67                                                                              +    99.6  75.2    195                            __________________________________________________________________________

EXAMPLE XXXI

A series of 1-hexene oxidations were carried out in the presence of 15ml distilled water, 1.5 ml 1N H₂ SO₄, 625 mg of polyoxoanion, and 1:5molar ration of Pd(CF₃ COO)₂ :polyoxoanion. An identical series ofcomparison oxidations were done having a 1:5:10 molar ratio of Pd(CF₃COO)₂ :polyoxoanion:CuSO₄ ·5H₂ O in the presence of 7.5 ml distilledwater, 7.5 ml CH₃ CN, and 1.5 ml 1N H₂ SO₄. All reactions were carriedout with 2 ml of olefin in R1's according to the general procedure. Thereaction conditions were 85° C. and 80 psig O₂ for 8 hours. The resultsare compiled in Table 5.

These runs demonstrate that the addition of a redox active metal and aligand can in most cases improve both conversion and selectivity. In allcases, one sees an increase in the number of molecules of ketoneproduced per palladium atom present.

EXAMPLE XXXII

A series of 1-hexene oxidations were carried out using a 1:5 molar ratioof Pd(CF₃ COO)₂ :polyoxoanion. Reactions were run in the absence of aredox active metal and a ligand and then compared to those in thepresence of a redox active metal and (or) ligand. The ratios ofsolvents:ligands:redox active metals were identical to those in ExamplesXXVII to XXXI. All reactions were carried out at 85° C. and 80 psig O₂for 8 hours. The results are compiled in Table 6.

These oxidations demonstrate that the addition of a redox active metaland a ligand can increase conversion and selectivity. It is furtherdemonstrated that, as expected from the theory, the effects of the redoxactive metal and ligand are not merely additive. In the case of PMo₆ W₆O₄₀ ⁻³, the additive turnovers per palladium would be 9. The observedeffect of both the addition of Cu⁺² and CH₃ CN is 145.

                                      TABLE 6                                     __________________________________________________________________________                            CuSO.sub.4                                                                             Hexene                                                                              Selectivity                                     Pd(CF.sub.3 COO).sub.2                                                                Polyoxoanion                                                                         [mol]                                                                             CH.sub.3 CN                                                                        Conversion                                                                          to 2-Hexanone                                                                         Turnovers                      Polyoxoanion                                                                           [mol] × 10.sup.3                                                                [mol] × 10.sup.2                                                               × 10.sup.2                                                                  + or -                                                                             mol % mol %   per Pd                         __________________________________________________________________________    PMo.sub.6 W.sub.6 O.sub.40.sup.-3                                                      2.53    1.27   --  -    4.2   9.1     1                              "        2.53    1.27   2.54                                                                              -    3.6   20.7    2                              "        2.53    1.27   --  +    24.0  7.7     7                              "        2.53    1.27   2.54                                                                              +    99.4  38.6    145                            P.sub.2 W.sub.12 Mo.sub.6 O.sub.62.sup.-6                                              1.60    0.80   --  -    5.2   29.3    9                              "        1.60    0.80   1.60                                                                              -    10.6  60.5    38                             "        1.60    0.80   --  +    25.9  18.1    28                             "        1.60    0.80   1.60                                                                              +    97.5  30.0    136                            P.sub.2 Mo.sub.18 O.sub.62.sup.-6                                                      2.13    1.07   --  -    17.5  48.6    38                             "        2.13    1.07   2.14                                                                              -    34.6  33.2    51                             "        2.13    1.07   --  +    48.5  43.8    95                             "        2.13    1.07   2.14                                                                              +    86.4  23.1    89                             __________________________________________________________________________

EXAMPLE XXXIII

A series of 1-hexene oxidations were carried out in the presence andabsence of the additives of the instant invention. The comparisonreactions were carried out at high stirring rates in R3 according to thegeneral procedure. The reaction conditions were 85° C., 100 psig ofoxygen, and pH 1.5. The volumes of solution and olefin were 39 ml and 2ml respectively. The catalyst components and their concentrations arelisted in Table 7, together with the results.

These runs demonstrate that the addition of a redox active metal and(or) ligand can improve conversion and (or) selectivity underindustrially acceptable process conditions.

                                      TABLE 7                                     __________________________________________________________________________                                               Selectivity                                Polyoxoanion                                                                         Pd(NO.sub.3).sub.2                                                                  Cu(NO.sub.3).sub.2                                                                          Conversion of                                                                         to                                         [mol]  [mol] [mol] CH.sub.3 CN                                                                        Time                                                                             1-Hexene                                                                              2-Hexanone                         Polyoxoanion                                                                          × 10.sup.2                                                                     × 10.sup.3                                                                    × 10.sup.2                                                                    %    min.                                                                             mol %   mol %                              __________________________________________________________________________    PW.sub.6 Mo.sub.6 O.sub.40.sup.-3                                                     1.03   2.06  -     -    20 21.4    58.2                               "       1.03   2.06  2.07  -    19 39.2    60.4                               PW.sub.6 V.sub.6 O.sub.40.sup.-9                                                      1.03   2.06  --    -    56 91.7    85.8                               "       1.03   2.06  2.07  25   21 92.5    87.6                               PMo.sub.6 V.sub.6 O.sub.40.sup.-9                                                     2.59   5.18  --    -    89 96.5    81.3                               "       2.59   5.18  10.4  40   16 96.4    87.0                               __________________________________________________________________________

EXAMPLE XXXIV

1-hexene was oxidized in the presence of 7.5 ml distilled water, 7.5 mlacetonitrile, 1.5 ml 1N H₂ SO₄ and PW₆ V₆ O₄₀ ⁻⁹. The oxidations werecarried out with 2 ml of the olefin in R1 at 85° C. and 80 psig O₂ for 8hours according to the general procedure. The amounts of the catalystcomponents and the results are shown in Table 8.

Table 8 also shows two 1-hexene oxidations in the presence of 15 mldistilled water, 1.5 ml 1N H₂ SO₄ and PV₁₄ O₄₂ ⁻⁹. The reactions werecarried out with 2 ml of the olefin in R2 at 85° C. and 80 psig O₂ forone hour.

These oxidations demonstrate that the product distribution, yield andselectivity are not a strong function of the palladium counterions,i.e., any one of a number of counterions can be used.

                                      TABLE 8                                     __________________________________________________________________________         Pd    Pd.sup.+2                                                                         Polyoxoanion                                                                         Hexene                                                                              Selectivity                                                                           Turnovers                                      Salt  [mol]                                                                             [mol]  Conversion                                                                          to 2-Hexanone                                                                         per Pd                                    Reactor                                                                            Anion × 10.sup.3                                                                  × 10.sup.2                                                                     mol % mol %   Per hr                                    __________________________________________________________________________    R1   SO.sub.4.sup.-2                                                                     2.77                                                                              1.39   36.4  45.1    7                                         R1   CH.sub.3 COO.sup.-                                                                  2.77                                                                              1.39   35.0  51.1    8                                         R1   NO.sub.3.sup.-                                                                      2.77                                                                              1.39   35.9  45.0    7                                         R2   NO.sub.3.sup.-                                                                      3.56                                                                              1.78   34.0  97.0    77                                        R2   CF.sub.3 COO.sup.-                                                                  3.56                                                                              1.78   33.0  99.7    73                                        __________________________________________________________________________

EXAMPLE XXXV

1-hexene was oxidized by palladium nitrate in the presence of a redoxactive metal and (or) ligand but in the absence of a polyoxoanion. Theamounts of solvent and catalyst components are shown in Table 9. Theoxidations were carried out with 2 ml of the olefin and R1 according tothe general procedure. The oxidation conditions were 85° C. and 80 psigO₂ for 8 hours. The results together with a comparison run containingpolyoxoanions appear in Table 9.

These examples demonstrate that the palladium reoxidation requires apolyoxoanion component. In all of the comparison runs not containing apolyoxoanion, palladium metal dropped out of the reaction solution.

                                      TABLE 9                                     __________________________________________________________________________                   Pd(NO.sub.3).sub.2                                                                  Cu(NO.sub.3).sub.2                                                                  Polyoxoanion*                                                                         Hexene                                                                              Selectivity                          Water                                                                             CH.sub.3 CN                                                                        1N H.sub.2 SO.sub.4                                                                 [mol] [mol] [mol]   Conversion                                                                          to 2-Hexanone                                                                         Turnovers                    ml  ml   ml    × 10.sup.3                                                                    × 10.sup.2                                                                    × 10.sup.2                                                                      mol % mol %   per Pd                       __________________________________________________________________________    15.0                                                                              --   1.5   2.92  --    --      7.7   22.9    6                            15.0                                                                              --   1.5   2.92  2.63  --      6.2   23.9    5                            7.5 7.5  1.5   2.92  --    --      36.6  26.8    33                           7.5 7.5  1.5   2.92  2.63  --      38.1  24.0    31                           15.0                                                                              --   1.5   2.77  2.63  1.39    52.4  88.4    145**                        __________________________________________________________________________     *[PW.sub.6 V.sub.6 O.sub.40 ].sup.-9                                          **Compare to first run of Table 9 showing 6 turnovers/Pd.                

EXAMPLE XXXVI

1-hexene was oxidized using the three different reactors R1, R2, and R3.The polyoxoanion used in this case was PV₁₄ O₄₂ ⁻⁹ prepared according toexample XXI. All of the reactions were carried out according to thegeneral procedure. Reactions in R1 and R2 were carried out in thepresence of 15 ml distilled water, 1.5 ml 1N H₂ SO₄, and 625 mg of PV₁₄O₄₂ ⁻⁹. R3 had slightly different conditions with 37.3 ml of distilledwater, 3.73 ml 1N H₂ SO₄, and 713.8 mg PV₁₄ O₄₂ ⁻⁹. Thepalladium:polyoxoanion ratio in each case was 1:5, with R1 and R2 usingPd(CF₃ COO)₂ and R3 using PdNO₃ ·3H₂ O. The oxidations were carried outwith 2 ml olefin: 16.5 ml solution at 85° C. and 80 psig O₂ for 480minutes, 60 minutes and 27 minutes, respectively.

The fourth entry in Table 10 shows that, in this example, the reactionrate does not depend on the palladium counterion since it is identicalto the second run except for using Pd(NO₃)₂ ·3H₂ O instead of Pd(CF₃COO)₂.

These oxidations demonstrate that the oxidation rate increasessignificantly as one increases the reactant transport with higherstirring speeds and better reactor designs (R1→R2→R3). This alsodemonstrates that one can obtain very good selectivities at reasonableconversions (33% conversion, 99.7% selectivity) without large amounts ofoveroxidation.

                  TABLE 10                                                        ______________________________________                                                        Hexene    Selectivity                                                                              Turnovers                                       Time     Conversion                                                                              to 2-Hexanone                                                                            per Pd                                   Reactor                                                                              (min)    mol %     mol %      per hr                                   ______________________________________                                        R1     480      66.3      91.3       17                                       R2     60       33.0      99.7       73                                       R3     27       84.4      90.2       338                                      *R2    60       34.0      97.0       77                                       ______________________________________                                         *Uses Pd(NO.sub.3).sub.2.3H.sub.2 O                                      

EXAMPLE XXXVII

1-hexene was oxidized using the three different reactors R1, R2, and R3.The polyoxoanions used in this case were P₂ W₁₂ Mo₆ O₆₂ ⁻⁶ and PW₆ V₆ O₄⁻⁹. The oxidations were carried out according to the general procedure.Reactions in R1 and R2 were carried out in the presence of 7.5 mldistilled water, 7.5 ml CH₃ CN, 1.5 ml 1N H₂ SO₄, 625 mg ofpolyoxoanion, and a 1:5 ratio of Pd(CF₃ COO)₂ :polyoxoanion. R3 hadslightly different conditions with 29.3 ml distilled water, 9.7 ml CH₃CN, 1.704 g P₂ W₁₂ Mo₆ O₆₂ ⁻⁶, and a 1:5 ratio of Po(NO₃)₂ ·3H₂O:polyoxoanion. The oxidations were carried out with 2 ml olefin: 16.5ml solution at 85° C. and 80 psig O₂, for 480 min, 60 min, and 30 min,respectively. The results appear in Table 11.

These oxidations demonstrate that the oxidation rate not only increasessignificantly with stirring rate but it can do so at the expense ofisomerization which accounts for the better selectivity observed in R3than in R1.

                                      TABLE 11                                    __________________________________________________________________________                       Hexene                                                                              Selectivity                                                                           Turnovers                                                  Time Conversion                                                                          to 2-Hexanone                                                                         per Pd                                       Polyoxoanion                                                                           Reactor                                                                            (min)                                                                              mol % mol %   per hr                                       __________________________________________________________________________    P.sub.2 W.sub.12 Mo.sub.6 O.sub.62.sup.-6                                              Rl   480  97.5  30.0    22                                           "        R2   60   85.0  23.0    110                                          "        R3   30   97.5  89.7    349                                          PW.sub.6 V.sub.6 O.sub.40.sup.-9                                                       R1   480  38.9  53.7    9                                            "        R2   60   36.0  56.9    72                                           "        R3   21   92.5  87.6    426                                          __________________________________________________________________________

EXAMPLE XXXVIII

1-hexene was oxidized using the preferred catalyst systems of the bestprior art in which halide ions are part of the catalyst system. Thesecatalyst systems were tested in R2 at the process conditions of theinstant invention, i.e. 85° C. and 80 psig O₂ for one hour. The catalystpreparations and the various concentrations of solvents and reagentswere taken from the literature as indicated in Table 12. The oxidationresults appear in the same table.

These examples demonstrate that the catalyst systems of the instantinvention are superior to those described in the prior art.

                                      TABLE 12                                    __________________________________________________________________________       Conversion                                                                           Selectivity                                                                           Turnovers                                                   Run                                                                              of 1-Hexene                                                                          to 2-Hexanone                                                                         per   Pd.sup.+2                                                                            Polyoxoanion    Co-Catalyst                    #  mol %  mol %   Pd    [mol] × 10.sup.3                                                               [mol] × 10.sup.2                                                               Co-Catalyst                                                                            [mol] × 10.sup.2         __________________________________________________________________________    .sup.1                                                                           10     80      6.7   9.6    -      CuCl.sub.2.2H.sub.2 O                                                                  165.0                                                                Cu(OAc).sub.2.H.sub.2 O                                                                8.5                                                                  HCl      19.5                                                                 CH.sub.3 COOH                                                                          114.0                          .sup.2                                                                           77     43      8.4   59.9.sup.6                                                                           30.6.sup.6                                                                           CTMABr.sup.7                                                                           1.2.sup.8                      .sup.3                                                                           37     70      114   2.08   20     -        -                              .sup.4                                                                           98     18      39.8  4.19   -      Fe.sub.2 (SO.sub.4).sub.3.9H.sub.2                                            O.sup.9  50.0                                                                 HCl      5.0                            .sup.5                                                                           25     96      79.1  2.77   1.39   CuSO.sub.4.5H.sub.2 O                                                                  2.6                            __________________________________________________________________________     .sup.1 Standard Wacker used in oxidation of ethylene to acetaldehyde.         Stanford Research Institute P.E.P. Report No. 24A2, Dec. 1976.                .sup.2 U.S. Pat. No. 4,434,082, Example 9                                     .sup.3 British Patent 1,508,331, Example 6.                                   .sup.4 British Patent 1,240,889, Example 1run 4.                              .sup.5 Instant Invention using PW.sub.6 V.sub.6 O.sub.40.sup.-9               .sup.6 Concentration in aqueous phase.                                        .sup.7 CTMABr=cetyltrimethyl ammonium bromide.                                .sup.8 Concentration using the total volume of solution (2 phases = 28.3      ml)                                                                           .sup.9 79.4% Fe.sub.2 (SO.sub.4).sub.3                                   

EXAMPLE XXXIX

1-hexene oxidations were carried out in R3. The previously reported bestpolyoxoanion system involved PMo₆ V₆ O₄₀ ⁻⁹ /Pd⁺². As a result, thissystem was compared with an identical catalyst system of the instantinvention except for the addition of a ligand (CH₃ CN) and a redoxactive metal (Cu⁺²). Both reactions were run according to the generalprocedure in a 40 ml volume using 2 ml 1-hexene, 85° C. and 85 psig O₂.In the case of the instant invention 33% of the volume was acetonitrile.The concentration of the various catalyst components and the resultsappear in Table 13. The oxidation to 2-hexanone is 5 times faster withthe additives of the instant invention. The yield of the desired productis higher at high conversions.

These runs demonstrate that the addition of a ligand and a redox activemetal can increase significantly the rate of reaction and selectityobtained by the prior art.

                                      TABLE 13                                    __________________________________________________________________________                         Pd(NO.sub.3).sub.2                                                                  Cu(NO.sub.3).sub.2                                 Run           Polyoxoanion                                                                         [mol] [mol] CH.sub.3 CN                                  #   Polyoxoanion                                                                            mol × 10.sup.2                                                                 × 10.sup.3                                                                    × 10                                                                          %                                            __________________________________________________________________________    1   PMo.sub.6 V.sub.6 O.sub.40.sup.-9                                                       2.59   5.18  0     0                                            2   PMo.sub.6 V.sub.6 O.sub.40.sup.-9                                                       2.59   5.18  1.04  33                                               Time (min)                                                                              16.0   48.0  89.0  142.0                                        1   Conversion mol %                                                                        81.6   91.4  96.5  99.1                                         1   Selectivity mol %                                                                       91     84.3  81.3  75.5                                         1   % Yield of                                                                              74.3   77.1  78.5  74.8                                             2-Hexanone                                                                2   Conversion mol %                                                                        96.4   99.0  -     99.8                                         2   Selectivity mol %                                                                       87.0   87.7  -     80.9                                         2   % Yield of                                                                              83.9   86.8  -     80.7                                             2-Hexanone                                                                __________________________________________________________________________

EXAMPLE XL

In order to compare the rates of oxidation of different olefins, andtheir selectivities toward the corresponding carbonyl compound,ethylene, 1-butene, 4-methyl 1-pentene, cyclohexene, 1-octene and trans2-octene were individually oxidized in R3 under identical conditions.The polyoxoanion used in these oxidations was PMo₆ V₆ O₄₀ ⁻⁹ preparedaccording to example I. All of the reactions were carried out accordingto the general procedure. The reaction conditions were 85° C., 100 psigtotal pressure and 2000 RPM without baffles. The solvent systemconsisted of 29.25 ml of water, 9.75 ml of acetonitrile and a few dropsof 36N H₂ SO₄, enough to guarantee pH 1.5 after addition of thecatalyst. The catalyst system consisted of 1.25 g of K₅ H₄ PMo₆ V₆ O₄₀·10H₂ O, 0.0589 g of Pd(NO₃)₂ ·3H₂ O and 0.9631 g of Cu(NO₃)₂ ·H₂ O.Each olefin was added at reaction temperature in amounts of 2 ml. Table14 summarizes the results.

These results demonstrate that under conditions of the instantinvention, high initial rates and selectivities are achieved for avariety of olefins. FIG. 1 shows that the decrease in relative rates ofoxidation of ®-olefins with increasing carbon number is much lessdramatic than in prior art systems, rendering commercial oxidation ofhigher olefins economically attractive. In FIG. 1, curve b representspublished information of the relative rates of oxidation of the variousolefins by the Wacker system (Smidt et al., Angew. Chem., Vol. 71, No.4, 1959 and Smidt et al., Proc. 6th World Petr. Congress, Section IV,Paper 40-PD9, Frankfurt/Main, June 19-26, 1963). Curve a represents theinitial rate of oxidation of the various olefins (see Table 14) relativeto the initial rate of ethylene oxidation, per mole equivalent of olefinin the feed to account for the proportionality of the oxidation ratewith the olefin concentration. Point A in this Figure is equivalent toan oxidation rate of 8.58×10⁻⁷ moles C₂ H₄ /sec ml for the presentinvention at 85° C., 8.21×10⁻⁷ moles C₂ H₄ /sec ml for commercial Wackeroxidation of ethylene at 110° C. (SRI PEP Report 24A2, "Ethylene toAcetaldehyde", Dec. 1976), and only 9.68×10⁻⁸ moles C₂ H₄ /sec ml forBelgian Pat. No. 828,603 (Example 1) at 90° C. These latter numbersdemonstrate that much higher rates are achieved under the conditions ofthe present invention.

                                      TABLE 14                                    __________________________________________________________________________     Olefin                                                                                         ##STR12##                                                                                ##STR13##                                                                               ##STR14##                                                                              Run Time min                                                                         ##STR15##              __________________________________________________________________________    C.sub.2 H.sub.4  8.58 × 10.sup.-7                                                                   7.10 × 10.sup.-7                                                                  82.7     60     100.0                    ##STR16##       7.57 × 10.sup.-7                                                                   6.84 × 10.sup.-7                                                                  90.3     172    89.9                     ##STR17##       2.43 × 10.sup.-7                                                                   1.92 × 10.sup.-7                                                                  79.0     258    80.0                     ##STR18##       3.23 × 10.sup.-7                                                                   3.15 × 10.sup.-7                                                                  97.5     142    91.9                     ##STR19##       4.58 × 10.sup.-7                                                                   4.16 × 10.sup.-7 *                                                                90.8     142    99.8                     ##STR20##       2.86 × 10.sup.-7                                                                   1.87 × 10.sup.-7                                                                  65.4     141    85.9                     ##STR21##       1.57 × 10.sup.-7                                                                   1.37 × 10.sup.-7 *                                                                89.5     278    84.2                    __________________________________________________________________________     *2-ketone + 3ketone                                                      

EXAMPLE XLI

In order to compare the rates of oxidation of different olefins, andtheir selectivities toward the corresponding carbonyl compound,1-butene, cis 2-butene and trans 2-butene were individually oxidized inR3 under identical conditions. The polyoxoanion used in these oxidationswas PV₁₄ O₄₂ ⁻⁹ prepared according to example XXI. All of the reactionswere run according to the general procedure. The reactions were carriedout at 85° C., 100 psig total pressure and 2000 rpm. The solvent systemconsisted of 30.0 distilled water, 10 ml acetonitrile and a few drops of36N H₂ SO₄, enough to guarantee a pH of 1.5 after addition of thecatalyst. The catalyst system consisted of 1.1526 grams of Na₈ HPV₁₄ O₄₂·10H₂ O, 0.0589 gram of Pd(NO₃)₂ ·3H₂ O and 0.631 gram of Cu(NO₃)₂·21/2H₂ O. Each olefin was added at reaction temperature in amounts of 1ml. Table 15 summarizes the results.

These results demonstrate that under conditions of the instant invention2-butene isomers react at least as fast as 1-butene, with highselectivity to MEK and high conversions. This again shows thesuperiority of the present invention over the conventional Wackersystem, where the relative oxidation rates of the butenes was found tobe: (1-Butene):(trans 2-butene+cis 2-butene)=1:0.29. (Smidt et al.,Proc. 6th World Petr. Congr., Section IV, Paper 40-PD9, Frankfurt/Main,June 19-26, 1963.)

                                      TABLE 15                                    __________________________________________________________________________                                                  Olefin Conversion                      Initial Rate of                                                                          Initial Rate of                                                                          Initial Rate     At End of Run                          Olefin Disappearance                                                                     MEK Formation                                                                            Selectivity      moles olefin converted                 moles olefin converted                                                                   moles MEK* formed                                                                        moles MEK* formed                                                                        Run Time                                                                            moles olefin fed                Olefin sec.cc solution                                                                          sec.cc solution                                                                          moles olefin converted                                                                   min   (%)                             __________________________________________________________________________    1-Butene                                                                             1.37 × 10.sup.-7                                                                   1.27 × 10.sup.-7                                                                   92.2       201   90.2                            Trans                                                                         2-Butene                                                                             1.65 × 10.sup.-7                                                                   1.60 × 10.sup.-7                                                                   96.7       261   95.7                            Cis 2-Butene                                                                         1.59 × 10.sup.-7                                                                   1.31 × 10.sup.-7                                                                   82.4       289   99.9                            __________________________________________________________________________     *MEK = methyl ethyl ketone                                               

EXAMPLE XLII

Cyclohexene was oxidized to cyclohexanone in the presence of 15 mldistilled water, 15 ml acetonitrile, 3 ml 1N H₂ SO₄, PMo₆ V₆ O₄₀ ⁻⁹, andin the presence or absence of copper ions. The oxidations were carriedout in R1 according to the general procedure. The oxidations were donewith 5 ml olefin at 75° C. and 80 psig O₂ for 4 hours. The result appearin Table 16.

These examples demonstrate that the addition of copper ionssignificantly reduces dehydrogenation, allylic oxidation and diolformation.

                                      TABLE 16                                    __________________________________________________________________________     Cu(NO.sub.3).sub.2                                                                   Pd(NO.sub.3).sub.2                                                                    PMo.sub.6 V.sub.6 O.sub.40.sup.-9                                                     ##STR22##                                                                           ##STR23##                                                                           ##STR24##                                                                           ##STR25##                                                                           ##STR26##                                                                              ##STR27##            [mol] × 10.sup.2                                                               [mol] × 10.sup.3                                                                [mol] × 10.sup.2                                                                mol % mol % mol % mol % mol %    mol                   __________________________________________________________________________                                                            %                     --     4.00    2.00    .08   20.2  7.4   .74   1.16     33.5                  4.5    4.00    2.00    .05   35.6  2.58  .25   .38      41.0                  __________________________________________________________________________

EXAMPLE XLIII

The corrosion testing of stainless steel 316 was carried out accordingto NACE Standard TM.01.69 (1976 Revision).

The corrosion studies were done in a 500 ml resin flask which wasprovided with: reflux condenser, trap, oxygen sparger, thermowell,heating mantle, temperature regulator, variable speed motor and a glassspecimen support system.

The SS316 coupons (3"×3/4"×1/8") were submerged in the reaction solutionand olefin oxidation was carried out at 85° C. and atmospheric O₂pressure.

Corrosion rates are expressed as millimeter penetration per year (mmpy)and were calculated as follows: ##EQU1## where weight loss is inmilligrams, area is cm² of metal surface exposed, time is in hours, anddensity in gm/cm³.

Table 17 shows three PdCl₂ /CuCl₂ Wacker systems at various chloridelevels and their corrosion rates after two hours run time. Entry 1 is asystem of the instant invention with a small amount of chloride. Nocorrosion was observed in the latter system and enormous amounts ofcorrosion were observed in the PdCl₂ /CuCl₂ systems. FIG. 2 shows a plotof the corrosion rate versus chloride (Cl⁻) concentration.

These corrosion tests demonstrate that chloride-free polyoxoanionsystems, or thos polyoxoanion systems with only trace chloridecontamination, show no corrosion of SS 316. Thus, the systems of theinstant invention can use cheapter materials of construction.

                  TABLE 17                                                        ______________________________________                                        Oxidation      Cl.sup.-  Corrosion                                            System         moles/liter                                                                             Rate (mmpy)                                          ______________________________________                                        PMo.sub.6 V.sub.6 O.sub.40.sup.-6                                                            0.004     0                                                    Wacker 1       0.35      293                                                  Wacker 2*      3.17      1223                                                 Wacker 3       10.87     1825                                                 ______________________________________                                         *Identical to system used commercially for oxidizing ethylene to              acetaldehyde.                                                            

It will be apparent to one skilled in the art that the use of additionalmaterials in the reaction mixtures such as other oxidizing agents andorganic solvents, provided that these do not substantially adverselyaffect the reactions, is not precluded.

We claim:
 1. An unsupported, aqueous catalyst system useful for olefinoxidation to a carbonyl product which comprises:(a) at least oneisopolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one redox active metal component, whereinsaid catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.
 2. An unsupported, aqueous catalyst systemuseful for olefin oxidation to a carbonyl product which comprises:(a) atleast one isopolyoxoanion component which is a member selected from thegroup consisting of the compounds which have the general formula:

    [Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one nitrile ligand, wherein said catalystsystem is substantially free of nitrogen compounds selected from thegroup consisting of nitric acid, nitrogen oxides and esters of nitrousacid.
 3. An unsupported, aqueous catalyst system useful for olefinoxidation to a carbonyl product which comprises:(a) at least oneisopolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; (c) at least one redox active metal component; and (d) atleast one nitrile ligand, wherein said catalyst system is substantiallyfree of nitrogen compounds selected from the group consisting of nitricacid, nitrogen oxides and esters of nitrous acid.
 4. An unsupported,aqueous catalyst system useful for olefin oxidation to a carbonylproduct which comprises:(a) at least one isopolyoxoanion component whichis a member selected from the group consisting of the compounds whichhave the general formula:

    [W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of Mo, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one redox active metal component, whereinsaid catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.
 5. An unsupported, aqueous catalyst systemuseful for olefin oxidation to a carbonyl product which comprises:(a) atleast one isopolyoxoanion component which is a member selected from thegroup consisting of the compounds which have the general formula:

    [W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of Mo, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one nitrile ligand, wherein said catalystsystem is substantially free of nitrogen compounds selected from thegroup consisting of nitric acid, nitrogen oxides and esters of nitrousacid.
 6. An unsupported, aqueous catalyst system useful for olefinoxidation to a carbonyl product which comprises:(a) at least oneisopolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of Mo, V, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; (c) at least one redox active metal component; and (d) atleast one nitrile ligand, wherein said catalyst system is substantiallyfree of nitrogen compounds selected from the group consisting of nitricacid, nitrogen oxides and esters of nitrous acid.
 7. An unsupported,aqueous catalyst system useful for olefin oxidation to a carbonylproduct which comprises:(a) at least one isopolyoxoanion component whichis a member selected from the group consisting of the compounds whichhave the general formula:

    [V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, Mo, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one redox active metal component, whereinsaid catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.
 8. An unsupported, aqueous catalyst systemuseful for olefin oxidation to a carbonyl product which comprises:(a) atleast one isopolyoxoanion component which is a member selected from thegroup consisting of the compounds which have the general formula:

    [V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, Mo, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; and (c) at least one nitrole ligand, wherein said catalystsystem is substantially free of nitrogen compounds selected from thegroup consisting of nitric acid, nitrogen oxides and esters of nitrousacid.
 9. An unsupported, aqueous catalyst system useful for olefinoxidation to a carbonyl product which comprises:(a) at least oneisopolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein M' and M" are members independently selected from the groupconsisting of W, Mo, Nb, Ta and Re: a, z and m are integers greater thanzero; b and c are integers; and a+b+c≧2; (b) at least one palladiumcomponent; (c) at least one redox active metal component; and, (d) atleast one nitrile ligand, wherein said catalyst system is substantiallyfree of nitrogen compounds selected from the group consisting of nitricacid, nitrogen oxides and esters of nitrous acid.
 10. An unsupported,aqueous catalyst system useful for olefin oxidation to a carbonylproduct which comprises:(a) at least one heteropolyoxoanion componentwhich is a member selected from the group consisting of the compoundswhich have the general formula:

    [X.sub.x Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, V, Nb, Ta and Re:a, x, z and m are integers greater than zero; b and c are integers; anda+b+c≧2; (b) at least one palladium component; and (c) at least oneredox active metal component, wherein said catalyst system issubstantially free of nitrogen compounds selected from the groupconsisting of nitric acid, nitrogen oxides and esters of nitrous acid.11. An unsupported, aqueous catalyst system useful for olefin oxidationto a carbonyl product which comprises:(a) at least oneheteropolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [X.sub.x Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, V, Nb, Ta and Re:a, x, z and m are integers greater than zero; b and c are integers; anda+b+c≧2; (b) at least one palladium component; and (c) at least onenitrile ligand, wherein said catalyst system is substantially free ofnitrogen compounds selected from the group consisting of nitric acid,nitrogen oxides and esters of nitrous acid.
 12. An unsupported, aqueouscatalyst system useful for olefin oxidation to a carbonyl product whichcomprises:(a) at least one heteropolyoxoanion component which is amember selected from the group consisting of the compounds which havethe general formula:

    [X.sub.x Mo.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, V, Nb, Ta and Re:a, x, z and m are integers greater than zero; b and c are integers; anda+b+c≧2; (b) at least one palladium component; (c) at least one redoxactive metal component; and, (d) at least one nitrile ligand, whereinsaid catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.
 13. An unsupported, aqueous catalyst systemuseful for olefin oxidation to a carbonyl product which comprises:(a) atleast one heteropolyoxoanion component which is a member selected fromthe group consisting of the compounds which have the general formula:

    [X.sub.x W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of Mo, V, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; and (c) at least oneredox active metal component, wherein said catalyst system issubstantially free of nitrogen compounds selecteed from the groupconsisting of nitric acid, nitrogen oxides and esters of nitrous acid.14. An unsupported, aqueous catalyst system useful for olefin oxidationto a carbonyl product which comprises:(a) at least oneheteropolyoxoanion component which is a membrer selected from the groupconsisting of the compounds which have the general formula:

    [X.sub.x W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of Mo, V, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; and (c) at least onenitrile ligand, wherein said catalyst system is substantially free ofnitrogen compounds selected from the group consisting of nitric acid,nitrogen oxides and esters of nitrous acid.
 15. An unsupported, aqueouscatalyst system useful for olefin oxidation to a carbonyl product whichcomprises:(a) at least one heteropolyoxoanion component which is amember selected from the group consisting of the compounds which havethe general formula:

    [X.sub.x W.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of Mo, V, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; (c) at least oneredox active metal component; and, (d) at least one nitrile ligand,wherein said catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.
 16. An unsupported, aqueous catalyst systemuseful for olefin oxidation to a carbonyl product which comprises:(a) atleast one heteropolyoxoanion component which is a member selected fromthe group consisting of the compounds which have the general formula:

    [X.sub.x V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, Mo, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; and (c) at least oneredox active metal component, wherein said catalyst system issubstantially free of nitrogen compounds selected from the groupconsisting of nitric acid, nitrogen oxides and esters of nitrous acid.17. An unsupported, aqueous catalyst system useful for olefin oxidationto a carbonyl product which comprises:(a) at least oneheteropolyoxoanion component which is a member selected from the groupconsisting of the compounds which have the general formula:

    [X.sub.x V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, Mo, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; and (c) at least onenitrile ligand, wherein said catalyst system is substantially free ofnitrogen compounds selected from the group consisting of nitric acid,nitrogen oxides and esters of nitrous acid.
 18. An unsupported, aqueouscatalyst system useful for olefin oxidation to a carbonyl product whichcomprises:(a) at least one heteropolyoxoanion component which is amember selected from the group consisting of the compounds which havethe general formula:

    [X.sub.x V.sub.a M'.sub.b M".sub.c O.sub.z ].sup.-m

wherein X is a member selected from the group consisting of B, Si, Ge,P, As, Se, Te, I, Co, Mn and Cu; wherein M' and M" are membersindependently selected from the group consisting of W, Mo, Nb, Ta andRe: a, x, z and m are integers greater than zero; b and c are integers;and a+b+c≧2; (b) at least one palladium component; (c) at least oneredox active metal component; and, (d) at least one nitrile ligand,wherein said catalyst system is substantially free of nitrogen compoundsselected from the group consisting of nitric acid, nitrogen oxides andesters of nitrous acid.